Access KNX over TCP

Hello.

I am trying to solve issue where I have KNX bus behind NAT with static public IP and forwarding is working, but UDP protocol is blocked by provider. (I called the provider, they told me there is nothing they can do, I know is stupid, so here we go) So I standing in front of issue that I cannot connect to KNX bus because is only over UDP port. Is here anybody who already solve this issue and is willing share the solution?

PS.: On site Jigsaw is not an option because is only two thermostat that controll two rooms. Time to time disconnection is acceptable because of NAT connection.