See www.arrl.org, search for fox hunt receivers. some amazing, cheap, effective ideas here. They should do what you want. I seem to recall one that had a circular pattern of 16 LED's on it to indicate the direction of the signal. With three of these you should have the redundancy to find...
The mutiple transmitter/receiver thing may be the most economical. Actually there is a "game" you can play called fox hunting. Its often done on amateur radio frequencies, but can be done at fcc part-15 frequencies as well - FM radio or AM radio band, or 915MHz, 2.45GHz, etc.
The...