I was thinking of adding a smoker Martin but I don't think that one of our tank ones would fit inside unfortunately

I have had a look around for some alternatives such as a smoker from model trains etc but the only ones I could find were a bit expensive for what it will do, as you say the battery to run it could be placed outside of it maybe in a crate or something, if I do come across a small enough smoker I will definitely add one
Cheers, Lee.