Not much choice these days in that size. The last one I got was from ebay. Its a Shimano UN300 which don't seem to have the greatest reviews. From a quick search I see wiggle have them. Well strictly speaking its a 123mm they sell but 0.5mm won't make any odds.
I've got one in the size you are looking for. It's an un53 in 73x122. Bearings are super smooth with no play. Decal is slightly lifting but other than that, really tidy.