Follow up to my earlier post about the Carsick Designs Slingset. I'm happy so far with the Slingset, it's very well made and fits well on the bike. There's an internal pocket that's good for tools etc. The top doesn't fold over, so it's not waterproof or anything, and it's not designed to detach and come with you. It's more to put other bags and items inside. It works well for loading with grocery bags and such. With the kids on the back, their legs overlap the bag area, so it's not great for lots of grocery bags AND kids at the same time. I can get their school items in there and drop them off, then go shopping, but there would be limited room for groceries after picking them up.

I'm having trouble posting attachments, so here is a link to some photos: https://photos.app.goo.gl/6QcaAwp3DGPS7tkf8

Same exact question here. I found a Reddit thread where someone recommended aftermarket Rad Slingset bags from Carsick Designs. Link: https://www.carsickdesigns.com/products/rad-slingset

My Rad Wagon order is still pending so I can't offer a review, but I have the Slingset on order as well, so I can tell you how it works in about a month!

-Thatcher