The Wheels on the model finally gave way and broke off after a lifetime of use, so here is a visually identical copy of it, with the modification of being solid instead of a shell, and made for a 2mm steel axel instead of the flimsy pin stock axel.

I did need to drill out the axel holes to fit the new 2mm rod, but after doing that it all fit together perfectly and other than feeling more solid than it did before, there isn't any change in functionality!

Note: Uploaded from my Thingiverse account originally at thing 3351297.