Yes, it does seem like the part is listed as no longer available in North America. Automatics were / are much more common in Japan and JP carparts still shows the part number as active. You will have to enquire to find out if it is still available. (you need to scroll down about half way through the page to find the part number).
http://jp-carparts.com/honda/part_d...&type=NSX&cartype=19668&fig=E&fig1=700&fig2=4
There are a couple of other companies that specialize in sourcing difficult to find parts for Japanese cars; but, the names escape me right now. You could also try the NSXshop (a Prime vendor).
https://www.thensxshop.com/
I have used him and found him reliable and his reputation as a Prime vendor is positive. I expect that he does not list the part; but, he may be able to acquire it for you.
If it turns out that the part is unavailable, having done wiring repairs and some partial fabrication I have the following suggestions:
1)
The minimum quality wire should be SAE J1128 with the SXL, GXL or TXL designation. Its rated to 125 C operation and I like the TXL which is thin wall insulation because it can be easier to fit in a repair area. The thin wall insulation also makes it more flexible. Avoid wire which only has the J1128 designation or no designation as it will typically only be rated to 85 C (or less). There are higher temperature / more expensive / harder to source wires available. Even the SAE J1128 TXL can be a little hard to source. Waytek sells it; but, in 250' or 500' minimum quantities; but, its only $0.05/ft for 18 AWG so $25 for a roll - reasonable. You do need to match the wire sizes so you may have more than one roll. The more exotic high temperature wire is significantly higher in price - Digikey can be a good source to check out.
2)
I recommend that the splices not be soldered. Soldering risks damaging the adjacent insulation and a solder joint hot enough to avoid a cold solder joint results in solder migrating up through the wire strands resulting in a section of wire that is inflexible and subject to fracture. Do not use the common insulated butt crimp connectors (too bulky and the insulating jackets are generally poor). I like to use un-insulated closed barrel butt crimp connectors with a separate sleeve of double wall heat shrink for insulation. This will result in a more compact joint. It also allows you to confirm the quality of the crimp because the connector is bare. It is more time consuming because of the two step process of applying the crimp and then applying the heat shrink. It also requires a specific un-insulated closed barrel crimping tool (or die) correctly sized for the crimp. Match your crimp sizes correctly to the wire sizes. Un-insulated closed barrel crimps will not be available at your auto supply store. Again, try some place like DigiKey or Waytek.
3)
The un split corrugated covering that Honda uses on its wiring is high quality material. The similar looking split covering from the auto supply stores is low quality and low temperature (typically 90 C or less). Do not use it. You can source flame retardant poly propylene split loom covering that is good for 135 C from Waytek and probably DigiKey and maybe McMaster Carr. The bad news is that you buy by the roll so you are into $60 - $100 depending on the size. Unless you are taking the loom apart and unpinning the connectors you will need to use a split covering for the repair area. You can secure the split loom to the original covering using something like GB silicone self bonding repair tape. In fact, if the repair areas are small, fitting a new loom covering can be a problem. In that case, you can use the GB repair tape as the external jacket if it is used with a 50% lap. The GB tape is UL listed to only 80C at 600 volts. That is a reflection of the UL standard. Its useful operating temperature is closer to 250 C. I have used it to wrap a complete loom. It is a self amalgamating not an adhesive tape (it only sticks to itself). Once it has been in contact with itself for more than about 30 - 60 seconds, its not coming apart. Wrapping it takes a certain amount of skill. The self amalgamating means that the tape will not unwrap when exposed to oil or gasoline, unlike conventional adhesive style PVC electrical tape which has no place in an engine compartment. The down side to the self amalgamating tape is that if you bodge the repair, there is no unwrapping to do a fix. The only way that it comes off is to slit it with a razor.
Setting up to do the repair correctly is a hassle because of the requirement for the correct tools and the need to source supplies which do not come in convenient quantities. I can understand that you may not want to do this yourself. I offer up the gory details primarily so that you can at least have an informed discussion about how the repair is to be done if you source the repair out to someone. I have seen some pretty flakey looking wiring jobs in cars (my NSX had some pretty egregious electrical work done on it by somebody). The engine wiring harness is probably the last place where you want poor quality work. An intermittent fault in the engine wiring harness could drive you crazy.
