Since you mentioned smaller, I have a smaller Neewer Flash, the NW-320, which I use with my A6000.
https://www.amazon.co.uk/Neewer®-NW320-Display-Speedlite-RX100II/dp/B00VE5HQ4I
For me, size was a significant factor, and this is about half the size of a regular flash.
Downside is the low guide number (32), so it's not particularly powerful (but significantly more than a pop up flash would be).
Other than that, it does everything a regular sized flash will do - and I can even use it off camera in dumb slave mode triggered by the pop up flash if I want (the A6000 pop up flash mechanism allows you to adjust it's position with your finger so it fires vertically, rather than forward - it's too weak to be useful as a bounce flash this way, but is enough to trigger the remote flash slave cell).
If size / weight is a significant factor, it's worth considering, otherwise, go for something more powerful.