After much searcing the last few days, I must warn you all that the Delta GR 050 grinder is a piece of s--t. I hadn't used mine in a while, and didn't realize the leftover grindings had dried in the bottom and formed a sort of concrete down under the wheel, basically gluing it in place. I had poured water into the trough and turned it on. The grinding wheel immediately shattered into 3 pieces. It is made of a very soft material, and the center is splined, so the torque of the drive shaft is sufficient that that little bit of leverage is all it takes to break it.
Oh well, I thought, I'll just order a new wheel. But, Delta's web site showed no parts could be ordered. Went to my local authorized Dewalt/Porter Cable/Delta repair place - he can't get it either. He gave me the toll-free number for Delta: "No, sorry, no replacement parts".
Googled all over, can't find anything similar size. Specialty shops want double the price of the ^%$@#$$!! machine to make a wheel. It appears Delta is now in the disposable machine business now. I will certainly be wary on future purchases!