You can rig something up for $100? How?

The cheapest 2M radios are about $150 after rebate. A decent antenn and an NMO mount will be close to $100. The GPS itself will run at least $50 used. You also need a TNC, which I have not priced lately.

With all that being said, I would be perfectly happy with a simple GPS, and a 2M with enough guts to hit some nearby repeaters.

For that matter, if the SAR team knew that you were a ham when looking for you, I would imagine that they would try to get you on 146.520. If they get within five miles of you in an aircraft, you should be able to work them.