try Galle motors for beedings, thats the only one i know and have seen a place near delkanda but dont know much about that place...
for wheels, Amila and JJ wheels in dehiwala and there are about 3 shops in slave island which has a good collection ...
btw alloys are bit expensive now, i went to check some last week and the prices were 15" in 40K range and 14" in 30K range .... i'll get only 10K for my old alloys...
hope this helps...