[drc]

I suspect a good working eBay account would count as one.

Also, if you know of anyone who's a dealer or well known collector, that would count as another. If you've bought on eBay, you very well may have bought from a well known seller and list that person.

If you don't have the latter, just try your eBay name and feedback number. The auction just house wants evidence you pay your bidding bills and such, and an eBay account is evidence of that.