There's a more straightforward option than self-hosting your zrok instance that works with a cheap VPS to enable a TCP or UDP proxy (like a port forward).
On the VPS, you run this to expose your private zrok share on a public port:
zrok access private {token} --bind 0.0.0.0:4321
If the backend has mode tcpTunnel then it will open a TCP port, and a UDP port if backend mode udpTunnel.
Ensure the VPS's firewall allows the bind port you choose for the correct transport protocol: TCP or UDP.