I went to dollar tree to find something to put in the bottom because cardboard wasn't good enough.
I ended up getting a gardening knee pad. It's a bit too long so I cut it down and put some of the scrap foam in the handle cut out.
It's much better now, the foam gives it support without being too hard and uncomfortable.
Bulk Garden Collection Foam Kneeling Pads, 6½x15¼" at DollarTree.com
I haven't been able to get a decent picture of Lola in the bag. I'm planning on trying the bag tomorrow and hopefully get a decent picture at some point.
Here's a close up of the fabric, the yellow behind it is the knee pad.