please don't suggest BTC unless you have a truly anonymous way to get it.
you can consider to sell your goods or services for Bitcoin. Anyway, we also accept ZCash and Monero which are designed to provide a rather strong layer of anonymity on every and each transaction. Even a Bitcoin wallet which is always run behind Tor provides some anonymity layer.
The problem you mention with prepaid and gift cards is not something strictly related to us: prepaid cards sold in a certain country may be restricted to be used only in that country, and of course we can't have sites in every country of the world. The reasons for which prepaid cards can be used only in the country where they are sold in are essentially based on anti money laundering considerations.