Hi Merrill,
I am new to the Forum and personally, think you should have had a reply by now.
Anyway, I have had good success mounting antennae to the cowl or front fender on my old pu truck. You should be able to do something like that for your HT. You could mount a small external 1/4 wave whip or 5/8s wave antenna and run the coax into the cab where you could connect to the rig.
With the small antenna systems available today, it might be rather inconspicuous and resemble a broadcast whip.
On the rear fender of an old Mustang, I once mounted a 2 meter GAM antenna that was secured with a UHF fitting to match the coax cable, then ran the coax through the trunk under the carpet to the front where I mounted the rig.
There are lots of options and by this time, you probably have come up with a working installation.
If so, what did you come up with?
Bill
KL7YB