You can use cash to buy gift cards, then fuel your account with 3rd party gift cards.
https://www.privateinternetaccess.com/pages/gift-card-payment
(Not the most economical, but a good way to bootstrap into a VPN if more traditional payments are not available)
Continue to buy VPNs while using other VPNs. Or use mullvad who apparently even accept cash in the post.
PIA takes bitcoin, i’ve used it myself before. easier, cheaper and less risky than sending cash in the post
You can use cash to buy gift cards, then fuel your account with 3rd party gift cards. https://www.privateinternetaccess.com/pages/gift-card-payment (Not the most economical, but a good way to bootstrap into a VPN if more traditional payments are not available)