Hi Alex, great to hear from you as was wondering how your little ones are doing. Getting spoiled I hope lol. The best recommendation I can give regarding wheels is to ensure you purchase at least a 15" to 16" wheel with no rungs or areas in which thier little paws, nails or legs can get caught into. Leo Braun makes a great wheel but it's abit pricey ($100.00 or more). Ed Wheels seem to be the brand alot of pd moms and dads recommend (reasonably priced). I also like the Joh Hopewell wheels which have a 16" size and very solid. Here is a link regarding wheels in general and also a few for purchase.
( information on wheels with purchase links) Very good link with good description of appropriate wheels
(14" wheel but a good one)
(15", but I dont care for the bars on it as risk of injury)
(16") ( I love this wheel)
I dont recommend the wodent wheel as it is very confining and also great risk of injury for priaire dogs in particularly if you have a Plump one lol although ok for smaller animals such as mice, etc.
Hope this helps. I had a diagram for a homemade one if your guy is at all good with tools and it's varily easy to make. I'll see if I can find it as I believe I saved it to a floppy. Also be sure your cage has doors that are at least 17 to 18" in order to get the wheel in and out easily. Mine never would get in the wheel to run but play with the outside of it (go figure lol)