You can’t get Fresh Cab in Canada anymore - at least you couldn’t when I tried earlier this year. So I ordered some from the US on Amazon.com.
In order to prevent mice from getting into your trailer in the first place, go through it very thoroughly and plug any potential entrance holes. I use stainless steel wool and
Pest Block expanding foam to try to plug up all the little holes. Look for places where wires, pipes and gas lines come up through the floor.
I also put cotton balls in ceramic mugs, and put several drops of Essential Oil of Peppermint on the cotton balls. I put the mugs and the Fresh Cab pouches in key places around there trailer where mice would likely gain entrance.
Damp Rid is also a great idea. I have vent covers on all our roof vents so I leave the vents slightly open to promote air movement and the Damp Rid helps control moisture when its not below freezing temps.