Oh it's not just me who is hauling a VESA mountable giant monitor? I will readily presume that's why you want to carry a VESA mount.
So if the question is, I have a 20" carry on monitor in my backpack, it's VESA mountable, what do I mount it on, I can help!
I can recommend two options: some graphics tablet monitors have VESA stands and at least the stand for the YiyNova tablets is available. This is pretty OK. Not great because I wouldn't really dare to use it at 90 degrees but close enough.
Another option is to use a K&M 19685 VESA mount together with a tripod. I found that the relevant K&M tripod is not stable enough the legs are too close for a 18" x 10" -- it falls along a diagonal. I have not yet bought a replacement because I am testing the YiyNova stand from above but I am eyeing the BEXIN M225S (also EOSCN ES-6 and probably a bazillion other names) because it's very small, the legs open very far and it claims to hold up to 8.8lbs and the ball head is removable which is quite good because it's the ball head is just wobbling problem for this purpose.