I use the 8" fire HD tablet. Others the 7". There were wall mounts available at one time - worth searching for. As far as price, if you are in the US, Amazon has refurbished and used units available.
Other than that, any that will run a tested browser will work (not all browsers play nice with Hubitat).
The fire does not support these; however, the native browser works fine.
Dave
PS - found the below site. Has some good info on fire tablet as Hubitat pad.