The missus and I just returned from the Pa Camping & RV Show at Hershey, Pa. We saw a display booth with lightweight scooters, named Crickets, that caught my eye. Here's the link to the website: http://www.ricksesv.com
These appear only to be offered as 2 seaters, but since they weigh only 170 lbs, I know your Avalanche would be up to the task of toting one of these in the bed (I was told the price is around $1,700).
On a side note, AS was well represented at the show. There were 2 Safari SE FB, 1 25' International with the Ocean Breeze interior (very very nice), and 2 Basecamps. One of the Basecamps was configured with the Kelty tent at the rear, and the other one had a quad ATV inside - this trailer was hooked up to an AS Interstate (rear dinette), very cool...