At one time when those iris tote were sold at cabelas, there was a bigger model that I'm sure they would fit in. I just suggested the vacuum bags since you said you were using a garbage bag. I knew they would be an upgrade. What about a bag like they use in fishing tournaments to bring the bass alive to the scale. They are reinforced with a thread grid pattern. There has to be a bag out there. You could use an old corn sack for strength then a plastic bag over that to seal it. Or something like those waterproof stuff sacks, but they won't be air tight. Just a direction to explore.