Correction: 66P507 chips for OBD2A (96-98) cost between $37 and $60 depending on where you buy them and how many you purchase. In addition to the chip you must purchase or build a programmer, and find a program. This isn't that tricky, but its not cake like OBD0/OBD1. The parts are One-Time-Programmable, and are pretty much a waste of money as far as I'm concerned.
A lot of the OBD2B ECUs (99-01) use the 66589, which has a pin-compatible flash replacement, the 66Q589. There are pictures of a Mugen N1 CTR-ish ECU on PGMFI that features a 66Q589 and the electronics neccessary to flash it.
I believe there are a handful of programs in some corner of PGMFI... Prob OBD2 section. The schematics for the programmer are also there.
OBD2 for the most part is a waste of time, at least now.