It's easy enough to make them yourself. Buy two of the 125mm wheels, get a couple of nuts suitable (ebay or a plumbers merchants will have them), drill the bore out to just short of the outer diameter of the nut, heat the nut up using a big soldering iron/gas torch/blue flame light/gas kitchen hob and then carefully press it in. Don't breath in the ensuing fumes and make sure the place you're doing it is well ventalated.

Been doing this myself to make some captive nuts on the new panels for boner, works a treat.