I just got a $15 shipped CB radio on ebay that worked great on the last SDJC run (I lent it to someone else for the run cause I already had a vehicle radio).
I'm planning on using it for spotting. My main CB is mounted in the Jeep, which is much more convenient to use and doesnt need batteries, and has better range, than a handheld.
But, if you want to get a cheap handheld, tips for buying one:
make sure its 40ch
skip ones that dont come with a cigarette lighter adapter, unless you dont mind swapping out batteries
a low power/high power switch is handy to save battery power
dont buy anything older than 1990 (skip ones without a digital display)
skip ones where the buyer doesnt explicitly say that it works great
make sure it has a stubby black rubber antennae, not a metal one that telescopes out to 6 feet (it should not be shiny at all)
go to ebay.com and put this into the search box:
cb radio (handheld, walkie, hand, portable)
then hit search
when it comes up, sort by price or add a price limit of $15
remember you can get a brand new one for about $45 so keep the price cheap or its not worth it