I've had varying success with just chopping down a 120 spool. I use quite a few box cameras myself, kodak duaflex, argoflex, brownie hawkeyes, imperial 620, target 620, among others.
One of my brownies will simply take a trimmed down 120 spool, the other one needs to have a 620 spool as the uptake otherwise it completely jams. The duaflex needs to be respooled AND needs a 620 uptake, same with the argoflex. The best way is to experiment.
I would suggest cutting down the 120 spool that your film is one, cut down a 120 roll for the uptake, and see what happens! The worst will be that it jams, and you'll have to take it in a darkroom.
Absolutely FABULOUS camera by the way, beautiful! I'd love to get my hands on one like that.