Camp insulation Help

Hey guys I've got a camp in the middle of the marsh that is essentially a metal shack kinda like a quanza hut on posts 10 feet off of the water. We noticed how unbearable it is to be in the camp during the summer when it is so hot even with two air conditioning units and in the winter when it is very cold it is impossible to keep the heat in from a small heater. We sprayed foam insulation all over the metal walls and thankfully the camp is only about 20 feet long and 15 or so feet wide but we came up short on our spraying. There is probably about a 5th of the metal wall on the camp that needs to be finished sprayed. We also walled in the front and back walls with the pink roll up insulation and covered with plywood. We have noticed a huge difference in keeping the cold air and warm air inside from the insulation but still when the sun comes out, it is noticeable that the remaining metal walls warm up the inside of the camp a good bit. I was wandering if you guys knew of a cheaper alternative to finishing the spray insulation other than spending another 500$-600$ on another purchase of spray insulation because we just don't need that much more. We would probably only us a 1/5th of that purchase to finish the camp. If you guys know of anything else we could do or find a smaller amount of spray foam insulation please let me know