Agree absolutely with the "buy a transceiver" advice. It may save your life some day. Otherwise, you may find yourself selling your scanner and buying a transceiver in a year or so.
Ideally, you need the "old model" Icom, which appears from time to time in "for sale" ads. There are serious problems with headset adapters with the later Icom models - Icom know about the problem, but either don't care or don't know how to fix it. (Unless there's new news in the last couple of months).
You absolutely do need a headset adapter - you'll never hear what's being said otherwise, if the engine's running.
Some transceivers are "legal" for use in aircraft, and some aren't. There's mostly no difference in performance - only in whether or not the manufacturer paid to have them approved by the CAA. For normal use (eg in a homebuilt or a microlight), you'll want to be legal. If it's only ever going to transmit in an emergency, it's up to you. Better in court for using an unapproved radio, than at the bottom of the sea.