I bought one of these back in June because the price ($29.95 shipped!!) seemed too good to be true:
https://www.amazon.com/gp/product/B00DCTCGW6/?tag=sxsweb24-20
Well it came in a couple days after I bought it, and it is amazingly nice. The other day I took my Honda bed off for cleaning and I decided to try this bag out. It's awesome! I might not put the bed back on till spring... This bag easily fits a 30 pack - probably 2 if you remove the dividers - and has plenty of room to spare. The day I put it on, I went riding and got caught in a downpour for over an hour. And the buggy was parked outside for a while in the rain too. I had a few things in the bag. When I finally got home, I checked and the inside of the bag was almost completely dry. The inner wall was just slightly damp - no puddles or anything. I'm sure when I use silicone tent sealer on the outside of it, it will stay bone dry.
Right now, they are out of stock and the price went way up. If you're looking for some kind of cheap cargo bag, keep an eye on this one. I bet when they get back in stock the price will be lower than it is now. I only bought it because the price was super low and it has a gun scabbard which I will surely use. There is an amazon review for the item from another Honda Pioneer 500 owner. I didn't review it on amazon. If the price gets back down anywhere close to $30, you absolutely can't go wrong with this bag.
I'll get a pic of it one of these days... or I guess it never happened.