15 X7's are almost as scarce as 15 X 8's. Most are 15 X6.
tell your friend to call Jimmy at Rally America. For $70 a piece for a brand new rim, with what ever width/backspacing you want, he's really hard to beat. Consider the time effort and cost of redoing one and you'll see what I mean
There are tons of 14" rims. I found some 15"x6 and some 15"x7. They are from mid '70's to early '80's GM. I'm putting them on my '37 Ford that has Chev disc brakes and Chev rear end. The odd thing is, '49 and up Ford hubcaps fit on the Chev centres. The wheels cost $25 each, $30 each to be sandblasted and $40 each to be powder coated. In the long run, it may have been quicker and cheaper to buy new wheels.