This may have been done before so I apologize if it has
I found a cheap source for a 9" Disc sander wheel. 19 some odd dollars
Sears parts dept.
Go to Sears.com and click on the parts menu.
(Couldn't get the link to paste for some reason.)
Type in Part # 351225950 for the Sander/grinder. This gets you to the machine itself.
Scroll down the list and click on part #8373.00 Alum. Disc
and part #1210.00 Set screw
If you register you can order online with a credit card.
Or you can call 1-800-366-7278 6am to 11pm CST. 7 days a week
I saw one at the store they look fairly well made!

I found a cheap source for a 9" Disc sander wheel. 19 some odd dollars
Sears parts dept.
Go to Sears.com and click on the parts menu.
(Couldn't get the link to paste for some reason.)
Type in Part # 351225950 for the Sander/grinder. This gets you to the machine itself.
Scroll down the list and click on part #8373.00 Alum. Disc
and part #1210.00 Set screw
If you register you can order online with a credit card.
Or you can call 1-800-366-7278 6am to 11pm CST. 7 days a week
I saw one at the store they look fairly well made!