Does your firewall have VPN options? If you're looking for something cloud-hosted then there's also NetBird, though it also uses Wireguard and will likely conflict with Tailscale. ZeroTier may not. There are numerous Raspberry Pi VPN options if you want, or already have, the hardware, and also this:
https://www.pishop.us/search.php?search_query=pikvm§ion=product