I went with a handheld Cobra - priced at about $80US.
No antenna mounting required for the simplest model, it has a quick connect
shorty antenna that's about 8 " long.
I just plug it into the cigar lighter with the DC power adapter (included) and I'm on the air.
I believe you can get a magnetic externally mountable antenna for it, but
so far I haven't needed it for what I use it for. It works just fine as is.
However in hindsight, I think it qualifies as a handheld communications device, like a cell phone,
as does the mic handle/cord for a fixed/built in CB, so there may be legal implications involved with
operating CB radios in some jurisdictions.
I suppose hands free CBs will soon be required, too.
They can be a lot of fun, and are a useful tool out on the road (traffic jam updates to name but one