That is a good question. Supposedly 500 were made, compared to, I think I recall, 10,000 242GTs imported into the US. But if you follow them long enough, there seem to flathoods everywhere. I bought mine recently from a nurse at the hospital I work at who had had it forever. "Flathood Denny" is a buddy nearby who has one. Pal Clay in San Diego has two of them. It seems harder to find a 242GT.
I think if you want a flathood and keep your eyes open for a quad light car with a funny looking grille (slanting back) and follow up on any '83 240 turbo ads and ask the owner if the car is intercooled. They are around and with a little looking they can be bought. Just don't buy a dud, because as soon as you do, the car of your dreams will come up for sale.