Eh, depends on how much you have to spend. I've made a fully functional wrist computer with the Raspberry Pi, and it only cost me around $120. And that's including a 32GB SD card (you only need 2GB, I just got a bit carried away), the keyboard, the monitor, the power pack, the material to hold it all together, and the little things like superglue and cardboard. A PipBoy has a more complicated case, but doesn't have a keyboard, so the price would probably be comparable.
Bethesda is selling those with the Limited Collector's Edition of Fallout 4, if anyone was wondering. It's hollow, but you put your phone in it and it syncs with an app they made that is identical to the in-game program (which you can get without said wrist band)
http://www.theverge.com/2015/6/18/8800037/fallout-4-pip-boy-wearable-e3-2015
Even if it was for sale the price would probably deter anyone
http://www.theverge.com/2015/6/18/8800037/fallout-4-pip-boy-wearable-e3-2015