I mounted a small 12V computer fan in mine. I zip tied it to a shelf in the fridge and ran the power line out through the hole that the drain line went through in the back inside of the fridge. Then, I simply spliced the power leads to a wire that carried 12V when the fridge was on. It wasn't hard to do. The PC fan requires very little current to operate and has been trouble-free for years.
I directed the airflow over the cooling fins below the freezer.
I think though, from what you are saying, that your fridge would cool down again if you waited long enough (12 hours or more). Are the items you are putting in already cold? This small fridge is not like your household one. It doesn't have a large cold space to compensate for anything that is not cold.
- Jack