My network currently looks like this (simplified):

Note that Router #2 is connected to the LAN interface of Router #1. This should be familiar to anyone who has seen a standard static-IP setup with an additional firewall for a residence or other small building. Router #1 is actually my cable gateway, but since it is a fully functional router/firewall, I am going to refer to it as a router.

Now, I need to open various ports in both firewalls for incoming communication to my server - port 80 is a good example. So I've opened up port 80 in Router #2, and so far all incoming traffic at the public IP X.X.X.129 is being routed correctly.

The problem is that I also need my server to respond to incoming traffic at the public IP X.X.X.130 on the WAN interface of Router #1. Naturally, I can't just tell Router #1 to forward port 80 to another public IP. Port forwarding is only supported when the traffic is being directed to the LAN subnet.

I am willing to restructure my network topology if required, with the following conditions:

Router #1 cannot have its WAN IP reassigned - X.X.X.130 is mandatory.  
Router #1 cannot be moved or disconnected from the cloud.  
The server cannot be given a second IP address.  
I would prefer the server to have a private IP address - e.g. 10.0.0.10  
I'd like to keep Router #2, but it can have a private IP - e.g. 10.0.1.10

Following these rules, I need to get my server to receive incoming traffic on port 80 from both public IP addresses. Does anyone on SU know if this is possible? So far my only theories have been to set up a static route on either router, or to somehow combine my two subnets into a single subnet.