You can get M3 replica bumpers from DDM Tuning for very little money. The quality is just as good as OEM, but they're way less expensive. Their customer service is very spotty, but the products are usually good. Alternatively, you can always find a used non-M bumper from a parts car on Craigslist or at a junk yard for pretty little money. Either way though, you'll have to find a body shop to paint whatever you buy. Installation is very easy - just gotta make sure you still have all the little screws to secure the underbody and fender liners.
1998 BMW 328is
1966 Pontiac GTO
2007 Subaru Impreza 2.5i 5-door
View my photos: Caught in the Wild