car-part.com is an aggregator for dismantlers. You can sort by distance. I always check AWD and RWD since it's just an oil pan swap, though RWD is usually cheaper. I also check N20 and N26 since for my purposes they're equivalent, and the N26 is usually cheaper. For a street car swap I think you have to swap the fuel supply line and figure out what to do with the valve cover air line that goes to the air intake somewhere.
Also be careful about getting a 20i instead of a 28i motor. The equivalency database that car-part and therefore a number of dismantlers use says they're the same. They aren't. I don't think there was ever an N26 20i motor which makes that route a little safer. You can tell by the etching on the block:
https://f30.bimmerpost.com/forums/sh...62&postcount=5