We use large, strong plastic zipped bags from Ikea to store large things aloft. They have handles and a couple (with very light items) are hung from hooks in the wooden rafters up there. Designed for bedding they are quite large. Might work? You could check the size on their site. I don’t have one handy to measure. I’m sure other retailers would have something similar or even larger.
We do have a battery rodent deterrent in the loft since an incursion some years ago. Also, I’m ashamed to say, two of those small mouse boxes, so far no residents, of course a humane trap would work as well. I own to being terrified of all rodents.