Check out this site http://www.salvage-cars-for-sale.info/ I found quite a few Miatas on there.. even a MINT condition Merlot with low miles and all original BBS with centercaps. It just had mechanical issues. The body and top were just fine though.
Buy an entire car cheap, take parts you want, and part out the rest.
cali way to far for me but nashville possible i found one in A1 salvage in huntsville very good body...idk y its there no motor or trans.. no front suspension but rear drive train there all body parts and all interior if any body needs!