Well to get started with you might try to use Moneybookers and iKobo. Both handle adult and are a paypal alternative. Also I think ePassporte offers something with a fee but I don't think it is an outrageous one.

Also sign up with paycom/epock for non VISA and then simply link VISA to iKobo or moneybookers for now. Worth a shot I'd think plus it gives you a backup.

iKobo isn't very good service/support but it costs nothing to sign up and their transaction fees aren't all that bad. Moneybookers gives better support.

hth
Ian

ps/ if you do set up an affiliate, let me know and I'll sign up.
Ian