You can use the search function on the forum to look at posts in the past. This subject has indeed been discusssed here a few times.
These are the cheapest (and original) bearings I bought in the past: https://www.ebay.co.uk/itm/24-6860-wheel-bearing-TRIUMPH-AJS-MATCHLESS-BSA-014868-K1178X-TIMKEN-/293681908092?_trksid=p2349624.m46890.l49292
I've just purchased some koyo HI-CAP 11590/20 these should be the right size on the inside but will required a shouldered liner on the inside. The shoulder will control the overall width. Not tried yet as I'm still collect parts to build the hub.
Rear hub
66-6105 nut (I might have one, nothing to check thread with)
66-6104 spindle (the one I have has the threaded end missing)
26-6689 washer
15-7051 dust cap
33-5530 bolt
Two suppliers used so far, first one mostly rubbish
second one about 50% useful.
More to turn up from Germany via a German friend due to supplier unwilling to send to the uk!
I don't think this is going to be an easy project.