Pocket dual-band router

I'm looking for a router that meets the following three criteria:

  1. Portable - size that can fit in a pocket, has a built-in battery it can run for some amount of time from.
  2. Dual-band - has two radio antennas that can operate independently. At least one should be 2.4GHz.
  3. OpenWrt friendly - having it support it out of the box is not necessary, but it should have a decently compatible chipset at least.

An example of a router that meets the first two criteria is ZTE MF928 - a tiny hotspot that can fit in the palm of your hand.

It has all the specs I need - and the size is very good, too. Unfortunately, the SoC on this one is Qualcomm MDM9207 - which has no mainline kernel support at the moment. That makes porting OpenWrt not an undertaking I am excited to commit to.

Is there a more poweruser-friendly version of this device the community can recommend?

There are many. Take a look at the gl-inet devices as and the tp-link tl-wr902ac.