Its just a refrigerator? Dry ice evaporates, you have to add more and thats tedious. If it gives you -55 thats really usefull. You can use a aspirator also but then you need more heat, say 50degrees in the waterbath, thats normally no problem, I have used that for a lot of chemistry. If you see a separate pump, then I dont think a pump is included. There are cheap pumps used for refrigerant istallations on ebay, even pre-owned. They can do the job.