[help] router for two LANs

Hi there, i`m looking, and looking and nothing ... seems that i`m not looking with the right terminology ... I`ll explain:

have two LANs, each with 10 computers, we denote:
LAN1 (192.168.50.XXX and /24 )
LAN2 (192.168.51.XXX and /24 )

I need a device, guess a router, to make the following:
-all computers from LAN2 to be able to access only one computer ( say COMP1.LAN1 ) from LAN1 ;
-all computers from LAN2, should only access LAN2 computers
-all computers from LAN1, should only access LAN1 computers
-only COMP1.LAN1 and COMP2.LAN1 should be able to access internet, through a gateway ...



i plan on setting the permission of ALLOW or DENY based on IP address, so layer 3, so a router; never thought of using a layer 3 switch.

I have some knowlegde of networking, CISCO .... but i need a solution not as expensive as cisco, i looked for an ASUS product, because I live in ROMANIA, and i don`t have access to so many brands like you do in the US.

May you please point me to such a product ? or maybe just the terminology i should look for !?

Thanks