1 1/8" hollow, or 1" solid are the largest i've heard about for the 1stgen.

i dont know who sells the best, or best price. i know there are several out there which can be ordered over the net. a search engine should turn up lots of hits for you.

the 1 1/8" hollow and 1" solid are supposed to be comparable for handling. the hollow is lighter, but may have a shorter lifespan. i have never seen a broken solid bar on anything. i have seen bent ones, and i've seen quite a few broken hollow bars on production vehicles (from internal rust).