Wiz, when you say "a full wiring loom to the ECU", do you mean from the engine to the ECU, or the body loom to the ECU? Also, there isn't such a thing as a 4SGTE. There's just a Rev 4 3SGTE.
Anyway, RPM garage has an original 1997 JDM loom for sale – pretty crazy prices though. I've bought a few things off RPM Garage, and never paid the orginal listed price, so I'd make an offer knocking quite a bit of what's they're asking and there's a good chance they'd accept it.
Each section is listed seperately and they seem to have two sets for sale:
The engine loom:
https://rpmgarage.com/index.php?id_product=1408&controller=product&id_lang=1&search_query=mr2&results=142https://rpmgarage.com/index.php?id_product=1274&controller=product&id_lang=1&search_query=mr2&results=142 The body loom:
https://rpmgarage.com/index.php?id_product=992&controller=product&id_lang=1&search_query=MR2+turbo&results=115https://rpmgarage.com/ind...+turbo&results=115 Another option is buying one off yahoo auctions in Japan, via Importmonster. That would work out MUCH cheaper once you found a listing for the right bit of the loom. Here's one of an unknow year (for a 3SGTE) with every single bit of the car's wiring, currently going for $69. (Postage and importmonster's commision would be on top of the price, but you can calculate an estimate for the total cost on the importmonster site.)
http://www.importmonster.com.au/view?url=http://page2.auctions.yahoo.co.jp/jp/auction/b248408067&thumb=https://auctions.c.yimg.jp/images.auctions.yahoo.co.jp/image/dr516/auc0302/users/6/6/3/5/khtauto-thumb-148791106493284226531.jpg&title=A197%20SW20%203SGTE%20MR2%20F%20BOX%2011%20z You friend could buy that, then have an auto electrician re-pin anything tha's not in the right place and still come out way ahead.