I used to be into R/C cars and trucks, and remember HPI racing and Traxxas being a couple of the bigger names out there, you might be able to find something on their online stores.The idea of tires got me thinking. Radio controlled (R/C) model trucks have all kinds of off-road tire designs and there's a fair sized industry for replacement parts. So I started hunting around. Our knob is 2" (51mm) in diameter at its widest point. I haven't taken mine off yet, so no idea how deep it is, because it fits partially into a depression. But it does protrude nearly an inch.
The video showing removal also shows that it's on a hex shaft, but there is no indication of size. Some of these R/C models use hex axles to drive the wheels. So the issue is to find a tire that fits in the depression, or that sits in front of the depression without rubbing on the dash plate. That's a function of wheel offset, language we all know well.
R/C trucks are sized in scale. To get 2" outer diameter truck tires, you need to be looking in the 1/18th scale range. Most of the truck tires in that range are going to have an outer diameter slightly over 2" but the next smaller size is 1/24th and that gives you a tire diameter of about 1.25" which is way too small. There are a lot of wheels/tires to choose from, with some unexpectedly good looks. None match the Rebel's wheels, but there are a number of tire options that look close. And you can get sets of 2 for as little as $6.
The hard part is knowing the exact measurements of these so that you don't have to order a variety before you find something that works and fits the shaft. Maybe someone out there has one of these little RC trucks, or has a kid that has one, that can check it out.