This happened to ours as well. I tried epoxying it back on, but as another posted stated, there is not much there to grab onto. So, I got a piece of flat aluminum stock from the hardware store. About 3/4" wide and cut it so that it was the full diameter of the wheel. I removed the broken hub, placed on the wheel and taped it down so it would not move. If you look at the "axle" it is hollow with a plastic divider. Eyeballing it from the front-side, I marked and drilled two small holes, about 8/32" through the hub and the alum stock. then I drilled a hole out on the rim of the wheel at each end. 4 brass screws and nuts hold it all in place and, Voila! Wheel fixed! (if this doesn't make sense, let me know and I'll post a picture.)
Now if I can just find a replacement drive motor, which failed a week after I repaired the wheel, I'd be happy.
I'm now going to do my best to avoid buying Polaris anything in the future. For what they are charging for their equipment, it should last much longer!
Bill W.