I've been using battery junction lately, my source for 20700s. IMRbatteries is the other site I've used a lot over the last couple years.
I'm sitting on extra vtc6 batteries, if you would like a few. I've switched to primarily 20700, have more than enough 18650 since they only get used rarely (I picked up four vtc6 just before switching to the 20700 format).
(Alternately I also have lg he4 that have only gone through a couple cycles. I really don't want to hang onto more than 4 of the he4 and vtc6, since my regular mods are all 20700, and I still have good lg UPS' on hand.)
Vtc5 is a good 20a battery, vtc6 is a good 15a, he4 is a good 20a,... I stick with lg, Sony, and Sanyo (love the Sanyo 20700b - a true 4000 mAh a long as you aren't trying to pull more than about 60W per battery).