Upload & Sell: On
I've used Outdoor Research straps to secure my travel tripod to my Domke F-2 bag. They work well and are available from outdoor retailers like REI.
However I was strapping horizontally on the bottom of the bag although the tripod was longer than the F-2. Your application is vertical and may not work unless you strap just two legs at the top, then extend the third leg slightly near the middle/bottom and strap directly under the twist/flip lock. That sounds awkward though.
You could also just sell the tripod and get a travel model, they're about 17-20" long...