Where does one find these bumpers?

 

i do believe they are completly interchangable, so any website that sells the bumperss, or you can try to find pieces on ebay or at junk yards

 

Er...kinda...
Mountings on side will not match up...bit goofy if sides are not done if I recall right...
So you may find doing more trim swaps are needed....
But junkyards are a good option on trims...bumpers are gonna be $$....even used, body shops ****** them up....side trim...not so much.
I get the feeling from the way you asked you question this is your first car....

 

First mini Yeah, wasn't sure if they were interchangeable and I didn't know of any sites sold them. As far as getting them from the r53 and doing a little body work, that's fine with me.

 

And you would need to modify the bumper for the exhaust.... It has been done...bumpers run $350 ish...plus trim parts and paint...so about 700$ painted for a new one plus the side trim....
Body parts are big...so shipping is usually an issue... Even body shops get bumpers from mini...so the dealer might be the best option due to shipping....

 

It's a relatively easy swap. For the exhaust, replace the R53 black trim pieces with R50 black trim pieces from 2002-2004 model year (bumper was redesigned in 2005)