Valve offers this for free:
https://partner.steamgames.com/doc/features/multiplayer/stea...
> Steam Datagram Relay (SDR) is Valve's virtual private gaming network. Using our APIs, you can not only carry your game traffic over the Valve backbone that is dedicated for game content, you also gain access to our network of relays. Relaying the traffic protects your servers and players from DoS attack, because IP addresses are never revealed. All traffic you receive is authenticated, encrypted, and rate-limited. Furthermore, for a surprisingly high number of players, we can also find a faster route through our network, which actually improves player ping times.