Thanks everyone. We tried fitting Bookah to an old fleece vest and the front leg-neck connection didn't seen to be working. And I checked all of the great recommendations online.
Since we're out in the cold tomorrow on peak, stopped by in Petco this morning and tried this jacket on Bookah in the store:
http://www.myoutwardhound.com/oh05346.html
It's designed as a dog's life vest, with ripstop nylon and a thin layer of foam insulation under the top half of the jacket. There is a belly band secured with velcro and then fastex buckles, and a neck/chest piece secured with velcro and a strap. At $29 it was too inexpensive to pass up.
Because it folds out flat, we can also use it as a pattern to tailor a fleece jacket with its outline.
I suspect the jacket will be too warm on mild days, but hoping it works out well for cold, snowy ones.
Alan