Surely you'll find something on one of these sites.
Another alternative would be to look for "Mom and Pop" gunstores who happen to have websites with an online inventory.
The process of buying a handgun online is pretty simple.
-find the gun you want and the person/store who is selling it
-verify with them they're willing to ship the gun for FFL sale to you
-find a local store who's willing to receive FFL shipment on your behalf
and if all of the above is ironed out:
-pay the original seller (gun price + shipping costs, handguns have to ship next day insured)
-inform local store to contact original seller to provide their FFL info ($10-30 fee to local store to their role as an FFL recipient)
-once shipment is received, purchase is executed as if local store originally had the firearm (fill out the forms, NICS check, etc).
The real catch is to not get ripped off due to shipping costs and FFL costs and to find a reputable online seller. Other than that, you can get one of these transactions to go through in as soon as two days.