Go to the nearest hardware store and ask for 5 gallon paint strainer bags. They should come 2 in a package. Use your 5 gallon pot and do a half-size batch all grain (2 1/2 gallon batch). You'll need the grains crushed and a decent thermometer that is accurate. You can use a small digital thermometer but something you can leave in the water/wort is nice to have. Use software to determine the temperature for strike water (it calculates the water temperature so when you add the grains your mash will be right at the temp you need). Stir the grains in well, cover and insulate (towel, blanket, sleeping bag, etc) and leave it for an hour. Pull the bag and drain it, squeezing out all you can and you've just done a no sparge BIAB all grain. Minimal expense, low investment in case it doesn't turn out good since you only used a small amount of grains (don't worry, it will turn out).