After having done way too much research on this topic over the last several years, I have come to the conclusion that you are best off simply buying these 2 bearings (AS205 and UB205) from your favorite Yamaha parts source as service parts. There are several that advertise on here.
I have studied the technical engineering data on the original equipment, and spent numerous hours with bearing suppliers cross referencing them to other manufacturers. I rarely found a supply source that could beat the prices in the small volumes (less than 1000) that we would be interested in.
The UB205 bearing was originally designed as a pillow block bearing, so it must be specially packaged for Yamaha as a service part. (similar to private branding)
Just remember that all 6205 bearings are not created equal, those extra letters indicate tolerances (important for cold temps), seal type and material, and any special specs.
I have a ton more tech info on these bearings downloaded, and my own theories written down somewhere, but I won't bore you here any more than I already have.
There are people that simply run the 6205's, in fact some large mail order houses list the 6205 as a direct replacement. However, I believe that Yamaha spec'ed the double set screw - attached - locking collar for a reason. I have seen the shaft after it rotated in the bearing, and the gears after too much end-play occurred.
I recommend the Yamaha service part. With a fair discount they aren't really that badly priced. For all other 6205's I like the NTN Formula series, as it seems to last the best. You can still get them for under $10.