No, no one makes a "pre-programmed" GMRS mobile radio.

There are, however, many commercial grade UHF mobile radios that meet
the FCC Part 95 specifications for GMRS.  You would need to pick one of
those, and either have it programmed, or program it yourself.  Since
they are commercial grade radios, they do not always have all the
flexibility to do things like change PL or DCS tones on the fly in the
manner that the consumer grade hand held radios let you change their
"interference eliminator" tones.  Prices are considerably more than the
consumer grade hand held radios.  Expect to spend $300 or more per
mobile radio, in addition to the antenna and antenna mount which can run
$40-$100 depending one what you choose.

Some vendors that sell what you are looking for:
http://www.theradioman.com/mobile1.htm

Be aware that none of the currently available Icom mobiles have the part
95 certification.  Kenwood does, some Motorolas do also.  You can often
find decent stuff on E-bay, but buyer beware.  Way too often sellers on
there mis-represent radios as being "GMRS" ready, when they are not.  
Any and ALL modified "ham" or "amateur" radios are NOT legal to transmit
on GMRS, no matter what the seller claims.  Also, not all commercial UHF
radios will work on the GMRS frequencies, some have frequency splits
that do not cover the 462.550 to 467.725MHz segment of the band.  Also,
if you are not really familiar with commercial radio gear, stay away
from e-Bay as it is really easy to get hosed.  Also, if you are not
really familiar with programming radios, it is much better to buy them
from a shop that can program them as part of the sale.

Good luck, and I hope you find what you are looking for.