What's to ruin? It will get a little sooty.
AntiGravityGear has inexpensive pots: http://www.antigravitygear.com/antigravitygear-3-cup-aluminum-non-stick-cook-pot.html
The classic cheap cook pot is the Walmart or Kmart grease strainer/pot, but both may be discontinued. Cost was about $6. Update — found it here: https://www.end2endtrailsupply.com/Stanco_Greasepot.html
I see orphaned aluminum pots from mess kits in thrift stores all the time– usually about $3.
I made a survival kit using a 1 liter wide mouth stainless steel water bottle. It is heavy for a water bottle or pot, but evens out when used as both. The one in the link below is 6.7oz on my scale. FYI, the lid threads are not compatible with Nalgene stuff.
http://www.planetzerogravity.com/water-bottles/1-liter-water-bottle.html
You just want one that has a lid that can be removed completely for use in the fire. Some wide mouth bottles have a plastic section with the threads. Guyot Designs, Klean Kanteen make suitable bottles too, but the price goes up unless you can find a used one.
You don't necessarily need a wide mouth bottle. I sought them out to use for survival kits, storing all the items in the bottle and getting water bottle, cook pot, water purification and storage container all in one.