Sometimes I find myself on my road bike near a store where I want to stop and get something - say some fresh fruit - to take home. But, I find I have no safe way to carry it.
I just ordered and got 4 keychain backpacks - these were from Sahalie, but they are sold out now - I got them for $6.00 apiece. One for each bike and one for the wife.
So, they are VERY small, fit in my wedge or my rear jersey pocket very nicely, yet expand to carry a fair amount and supposedly up to 25 lbs. (but I don't think I would put that much weight in there). They have straps for over your shoulders.
Anyways, I thought someone on the list might be interested. I also have 3 larger foldable backpacks, but they take up a fair amount of room.
They are available - at a higher price - at Amazon.