One solution would be to include the affiliate code in your link. I know how to do this with CCBill, and some of the NAT's programs.. Like this:
http://refer.ccbill.com/cgi-bin/clic...in.com/gallery
Cookie gets set and you get credit regardless if the user types in the URL.
Pain in the ass to do it this way, but it would ensure you're not losing sales to type-in's..