Try "whitesewingcenter.com". I have spent months looking for this part. I live in Australia and am going to have trouble getting my money to him, (he doesn't accept PayPal, Direct Debit, Credit Cards or foreign cheques!) but you won't have a problem. Under "Elna Parts", you will find:
"#P220777-- New Elna supermatic friction wheel to fit type 722010 models . If your Supermatic is noisy, it is usually the 50 year old friction wheel causing the problem. Includes a free 4 page instruction booklet, with illustrations, for easy installation---$24.00"
Hope this helps.
Ann Noble, March 2010