I know that eprocessingnetwork.com is (or at least, has historically been) adult-friendly and has an authorize.net compatibility mode, so any shopping cart or windows-based application that is compatible with authorize.net should work seamlessly with eprocessingnetwork.

There are some other off-brand gateways that are adult friendly as well but the names of them aren't coming to mind at the moment. One is in Australia and another in Germany, and I think there are a couple more small companies in the US.