Firstfives.org

Im trying to get a rubber e12 rear spoiler, rare and expensive, the e21 looks kind of the same shape on the lip of the trunk lid, and about the same width, anybody got an e12 and an e21 rear spoiler they can offer up, im thinking the e21 item may be easier to get hold of.

Short answer: No. Close enough to fool you with e21, e28's but they don't fit right on all nice and perfect. Best answer is to wait patiently for one, in very good condition, to appear in classifieds or eBay. Usually $150 will get it, or more if you're willing. Not recommended: getting panicky you'll never see another, buying the cracked, crunchy one to fix up.

The hard foam versions, non e12, will be very difficult to cut, sand to fit. Glass is possible, but sanding the long curves, filling the tight ones isn't quick and easy. If you insist, at least try before you buy.

JoshInAtlanta has a BBS one for an E12.