While it's not 26650 compatible and assuming that you're not talking about a li-ion/NiMH charger that doubles as a USB power bank, I bought this one:
http://lygte-info.dk/review/Review USB battery box 4x18650 Ruinovo UK.html
For $32 and change, it came with four Sanyo UR18650FM cells and works quite well. Mine charges up an Apple 2.1A iPhone 6s and an iPad 2/3 on either of its 1A or 2.1A ports.
Swapping cells takes a little time and it's not something that you're going to open up and drop in new ones in 2 minutes, but it is a quality charger that's not much bigger than a deck of cards.
With today's 3500mAh cells, that's a capacity of 14Ah, so 7Ah useable at a 50% DOD.
Chris