There is nothing available as small as the "flashq" that works as a flash.
The Canon 90EX as it is the smallest flash available that is fully compatible with your 5D Mk II. It has just a little less power than most built-in flashes
Power: Guide No (ISO 100) 30'/9m (at 24mm)
Size: 1.7" x 2.0" x 2.6"
Weight: 2.570 oz. with two AAA cells
(1.8 oz. empty)
The 270EX or 270EX II is also fully compatible with your 5D Mk II, is only slightly larger, but has much more power. It also recycles faster and has a tilt-up head for bounce flash.
Power: Guide No (ISO 100) 89'/27m (at 50mm) 72'/22m (at 28mm)
Size: 2.6" x 2.6" x 3.0"
Weight: 7 oz. with two AA cells (5.6 oz. empty)
The 220EX is also a pretty good option. It recycles faster because it uses 4 AA batteries but that also makes it a little bit larger and heavier.
Power: Guide No (ISO 100) 72'/22m (at 28mm)
Size: 3.6" x 2.6" x 2.4"
Weight 9.0 oz. with 4 AA batteries. (5.6 oz empty)