I recently purchased my 1991 NSX that has a set of 97-01 installed but the sale included the original wheels that needed to be refinished. I searched for wheels to compare the cost to purchase replacements vs. refinishing the originals and there are plenty available on EBay and other OEM wheel sites. However, finding the center caps was the tough part. I got lucky and negotiated the purchase of just the center caps from one of the OEM wheel sites but the set cost me $200! Thankfully they are in great shape and I've since had the original wheels refinished for another $450.
After buying the the center caps, I did hear from one member who said he may have a set of center caps available so if you need a set, let me know and I'll put you in touch with him. Good luck with your search.