2-arm VPN router behind Socket

I have a Cisco router from a 3rd party provider that provides access to that 3rd party providers networks. Thie router uses a 2-arm configuration with WAN and LAN interfaces.  The WAN cannot be a public routed IP, it must be a private IP.   

The router's existing deployment has the WAN interface connected to a DMZ zone off our legacy firewall, which uses a subnet of 192.168.1.0/24 and the router's LAN interface is connected to a trusted LAN subnet of 172.29.1.0/24.  The firewall does not have any inbound ports open to the VPN router's WAN interface, as the router is configured to outbound initiate the VPN tunnel.

I need to move this router to sit behind the socket so I can remove the legacy firewall from our network.  What would be the best way to set this up? Note that VLAN's are terminated to a L3 switch at this location, and I am not looking to move them to the socket at this time.  I would also prefer to not have the 192.168.1.0/24 subnet advertised to the entire Cato network (especially ZTNA clients).