Here's a latching relay circuit like the one Hotwaterwizard described.
You can use any DPDT relay for this, as long as your battery (BT1) can provide enough current to actuate the relay. Press switch S1 to activate the relay, press S2 to de-activate it. Use the second set of contacts in the relay to operate your lights, buzzer, etc. You could probably build a circuit like this and put it in an enclosure for $10-15 US each.
I'd probably use a 9v battery (maybe even a 9v lithium) instead of the rechargeables, they would probably turn out to be a maintenance headache. 9v lithiums are about $10 US each though.