I realize this post is almost a year old, but I thought I’d reply anyway.
I had the same problem with a used refrigerator someone gave me. I was literally the worse thing I had ever smelled — I couldn’t get the stink out for anything! I ended up calling a chemical company close by and asked them what I should do. Here’s what they said. Clean all the surfaces with white vinegar and baking soda. Then take Newspaper and crumple it up and use as much as you can. Take charcoal briquettes (the kind that is PLAIN — don’t use the stuff with the litghter fluid in them) and put them in with the newspaper. For the refrigerator I used about 30 or 40 briquettes. After I got everything in the fridge, I closed it up for about 3 or 4 days and didn’t open it at all. Once I opened it and got all the stinky paper and briquettes out, the refrigerator was as good as new! The stink was completly gone!
For a camper, it’s going to take a LOT of paper and charcoal, but it’s a pretty cheap remedy.