comments:
https://www.amazon.com/dp/B0BX68VZRW?ref=ppx_pop_mob_ap_share I like this one. It's low profile enough when zipped down that it doesn't interfere with my backpack as long as I don't have to much in it. But it expands quite a bit, and I can put a pretty large lunch bag in it and still have room. And while always keeping my Frogg Toggs and jacket liner rolled up tight in a Ziploc bag, and keeping "waterproof" gloves in the "lid" at all times in case I get caught in an unexpected rain. And even without using the rain cover, everything starts nice and dry. The straps did take some minor finagling, just because of where my seat latch is. But it came with everything I needed. And unlike other bags I've tried in the past, it doesn't get loose over time.