I looked online and several places show a superceded number. Those are available - $50 to $80 each. By the time special washers, bearings, pinions etc are also purchased, I'll bet the bill will be close to $200. If you love it, then it will be worthwhile. If it is worn out and beat up otherwise might be time to consider a new mower. Realizing it took me less than 5 minutes to find that the part was superceded, you might want to chase a new mower instead of chasing parts. Just saying. You aren't going to find a pair of $25 wheels for it.
ALSO - there are four 10641 variants listed. Make sure you have the correct one if you order parts.