Ask HN: Economical solution for static IP address?

The rural ISP I use originally set my fiber connection up to include a static IP address and ostensibly "business service". Yet, in the last couple of years they have redone their infrastructure and after some working with them, the IP is more stable than previously, it's still no longer static. Renting/purchasing an IP from my current ISP isn't an option as they have a limited number.

What are the options for having a static IP that isn't tied to the ISP? I have a machine I am hosting here and don't want to change that. My bandwidth is sufficient, it's just the IP that I need to figure out.

My current setup is an Asus router with port forwarding rules to a Linux server. Realistically, it will need to be some sort of tunnel or VPN to the linux machine itself.

I've seen VPN providers that can add a static IP for a price. I've got a couple of machines I am hosting on assorted providers that have IPs I could setup a persistent SSH tunnel/etc to, but that would incur bandwidth costs.

Are there any recommended options?