|What you could do, is to connect the two routers physically with a crossover cable from LAN port to LAN port. Both routers have IP's within the same subnet so this will work.|
However, if you're going to do so the best way to go about it is to disable DHCP on one of the routers. Two DHCP servers in the same segment is overkill and apt to cause problems.
Since you have to separate internet connections I'm going to assume you need certain clients using one, and the rest the other. If it were me, I'd pick the router with the least number of clients connected to it and give them all static IP addresses pointing at that router as the gateway. The rest, set to DHCP and they will automatically go to the other
Modem A (DHCP clients)
LAN IP: 192.168.0.1
Subnet Mask: 255.255.255.0
DHCP Enabled = Yes
DHCP Scope = 192.168.0.100 to 192.168.0.199
DHCP Gateway IP (as given to clients) = 192.168.0.1
Modem B (Static clients)
LAN IP: 192.168.0.10
All clients connecting to this device are to be given static IP addresses. Since your DHCP Scope is 192.168.0.100 to .199 you will want to use IP's outside that scope so as to avoid duplicate IP issues. I would recommend using IP's in the 192.168.0.50 to 192.168.0.99 range leaving 192.168.0.1 through 192.168.0.49 for any network devices like routers, printers etc. Ensure when configuring TCP/IP settings on all Router B clients you give them router B's LAN IP (192.168.0.10) as their Default Gateway address. This way all their internet traffic will pass through that connection.
Setup this way, no matter where you plug that printer in, all clients will still be able to print to it and you won't have to move the printer's network connection around ever again.
Alternatively, you could get a dual WAN router, connect both internet connections to it's WAN ports and all clients to it's LAN ports.
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.