Several months ago - many took advantage of Lowes' dropping a lot of Delta gear. A few grabbed the Delta GR-050 for $20. One person had the wheel shatter.
Rumblin' through Sears, I saw they had their version of the GR-050. For $25. I can't see replacement wheels online, but if you own a GR-050 and can't find a replacement wheel, maybe calling Sears is worth a shot.
Craftsman Utility Sharpener
Sears item #00921170000 Mfr. model #21170