With lnvpn, you can get down to a single hour's worth of VPN access https://lnvpn.com/
Mullvad supports on-chain bitcoin as well, and this site allows you to top-up mullvad with lightning. The lowest they go is 1 month though, so not as "pay per use" as lnvpn.
There are VPNs you can pay for with lightning!
With lnvpn, you can get down to a single hour's worth of VPN access
https://lnvpn.com/
Mullvad supports on-chain bitcoin as well, and this site allows you to top-up mullvad with lightning. The lowest they go is 1 month though, so not as "pay per use" as lnvpn.