i have had a few. Ended up selling all of mine as i needed money for bills n such at the random times ive sold them, except the one i dismantled to use the parts as ILM did on my own personal suit. I do plan to get another one to keep intact.
To answer your questions, They are hard to find, but not SUPER RARE, they do come up on e-bay from time to time. They usually range from about $85-$150 depending. I have seem them go for as little as $35 bucks on occasion though....timing is everything i suppose lol.
A few prop makers here (including myself) make replica key pads and circuit boards off of the real MQ-1.
It really is pretty cool how they used so many parts off of models and electronics for alot of the suits in the Star Wars universe. Everything from IG-88's head, to the "t-bits" on biker scouts bi-cep armor. So many things, and very cool to discover, and even cooler to obtain and use on your own suit!