As ably noted by
@drew, the low cost solution would likely be rebuild at home. It is typically the contacts on the solenoid that fail. Sometimes, you can pull the solenoid apart and touch up the contacts with a file and it will restore operation; however, there is a fair amount of grunt involved in removing the starter so if it were me I would definitely be putting in new contacts for the solenoid. If you don't want to do this yourself there are starter motor rebuild services that can do it for you.
Sometime during the pandemic, the supply for rebuilt starters and alternators for the NSX went dry so the chances of sourcing a rebuild are probably close to zero. Denso North America no longer lists the starter as available' probably because they don't sell enough to stock them. The good news is that just because Acura in North America no longer lists the starter as available doesn't mean that it is not available. Amayama.com currently lists 31200-PR7-A01 as being available and at a price much lower than that from North American based sources. They are a very reliable vendor (my go-to for all NSX parts) and have very reasonable shipping cost. Order today and you will probably have a new starter in two weeks.