I used to have a in-car cell phone system and it had a glass-mount
antenna which didn't require drilling. Basically, there was
coax(conntected to the cell) to a plate that stuck to the inside of the
rear window. Then on the outside of that window was another plate with
the antenna attached to it. You can buy these a radio shack I noticed.
I've also seem the same done for XM/Sirius Satellite radio.

I have searched and searched and so far have not found the same thing
for 2.4 ghz wifi. Does anyone know where I can find one? If not,
could it be as simple as removing the cell antenna from the exterior
plate(of the radio shack cellular version) and reattaching a 2.4 ghz
omni? Or maybe I could modify the existing cell antenna to the correct
1/2 wavelength of 2.4ghz?

Your suggestions / help / tips are appreciated.

-Kevin