Put a post on Craigslist in your local area. Make the add say say something like "Looking for a broken upright freezer in good shape I'll pick up free of charge"
Buy some big apple heat cord and use a hot glue gun to secure it along the sides and back. Drill 3 holes in the side of the freezer one for the heat rope exit one for the temp probes and one for the heat controller probe. Put a good temp controller on the top of it. If you dont breed alot of snakes just use a mini fridge.