Hi Tad
As well as Ubiquiti, you might also look at products from Open Mesh (
openmesh.com) and Mikrotik (
mikrotik.com). No doubt there are also other manufacturers as well.
If you can get suitable OpenWrt based routers you can set them up to mesh fairly easily.
GL.iNet (
gl-inet.com) have a range of small OpenWrt based routers and have recently released a meshable dual band router GL-B1300.
Dragino (
dragino.com) have manufactured VT hardware in the past and offer several meshable OpenWrt based routers.
Be aware that manufacturers of APs using proprietary firmware have
introduced measures to prevent installation of third party firmware like
OpenWrt, so you need to be able to use the OEM firmware for your
deployment.
One of the challenges you may face is the power consumption of
typical commercial devices, particularly if they are using 5GHz as well
as 2.4GHz.