Where to buy sanding plates

[Scimonetti]

I am looking for a 9" sanding disc with a 5/8 arbor and set screw. I bought one for $20 on ebay a while ago, but it is cheap pot metal and doesn't run true enough to sand.

I have been unable to locate anything online, can anybody help me out with this? I'm pretty stumped, even using the word back plate.

 

[Fluxion]

Here's a couple places to buy the same disc, these are really nice BTW.

http://www.beaumontmetalworks.com/shop/item.aspx?itemid=8

http://usaknifemaker.com/grinders-sanders-all-kinds-c-99/disc-flat-9-aluminum-t-6061-5-8-bore-for-disc-grinders.html

You posted again while I was typing! Sorry, I guess the ones I linked are probably too expensive.