You need a router with two LAN interfaces. Any Cisco model would do the job here.
http://www.cisco.com/en/US/products/hw/routers/index.html
One LAN interface should be assigned under the 192.168.200.0/24 network and another LAN interface should be assigned under the 192.168.201.0/24 network.
You should have an ip route in the Cisco router like this:
ip route 0.0.0.0 0.0.0.0 192.168.200.1
and the clients in the 192.168.201.0/24 network should point to the Cisco LAN interface as their gateway.
For instance if the LAN interface that is connected to that subnet is 192.168.201.254/24 then that's the gateway for devices on that subnet.
Also, 192.168.200.1 device needs to know how to send the packets back so it needs a route like this:
ip route 192.168.201.0 255.255.255.0 192.168.200.254
192.168.200.254 being the Cisco Router LAN interface for that segment.
HTH,