Based upon that I will probably invest in a new pair of panniers, as I used mine also heavily for grocery shopping.
I was thinking of something like the box in the picture - should still be portable on a bike and apparently you do not have to hang it.
Have a nice 2023 !
Depending on your budget - you can always wash soiled panniers. On the other hand - for most folks, any excuse to replace worn equipment prior to a big trip should be used.
Although carrying one's own bear-proof container saves some time and is a must in the treeless areas of Alaska or among the well-trained camp robbers of some of our national parks, they are bulky, cumbersome, and can be costly compared to a waterproof bag and 50 feet of paracord, to be used when campsite boxes are not available. Of course, I pitched baseballs as a kid, and still enjoy the capability of accurate rope throws over branches.... Some folks find this practice an exercise in futility. In the end, we've all tried a bunch of different ways to keep our food and toiletries away from critters big and small; everyone develops practices that work best for them.
If you search the forum for previous threads, you'll find plenty of additional advice and options and references to reviews in some of the American magazines that cater to backpackers and off-road "bike packers."
Have fun.