FRS & GMRS radios are sold everywhere,Sporting Goods,Most department stores and even wallyworld. They are hand held and battery operated.
Motorola, Cobra, Uniden, and most every maker of Cb's manufactures them. Normally sold in pairs and many have charging bases with rechargeable batteries.
Here is a set from best buy
http://www.bestbuy.com/site/olspage.jsp?skuId=8804582&st=GMRS+radios&type=product&id=1209165019958 .....or
http://www.bestbuy.com/site/olspage.jsp?skuId=8824533&st=GMRS+radios&type=product&id=1209165020688
Watch for them on sale, I've seen them for $20 at Home depot.
They can have a very long range and each channel will have many 38 or more privacy codes which allow you to talk without much outside interference.
Use of some of the Hi power or long range channels may require a licence.