Ok, I'll try to explain this. I don't know if it will make sense. Here goes.
If you want to put 2 handles on you put your outside piece RSU, then one handle on top of that where you want it, then the zipper RSD on top of that and then the lining RSD on top of that. Pin them all together, sew and flip around and repeat for the other side. Does that make sense?
No. I'm pretty sure they don't carry any designer fabrics. Actually, I've seen a few Alexander Henry in their novelty, skulls and such, but never Heather Bailey. If you have a quilting fabric shop in your area, you might try them. I have 2 near me and they get a lot of the designer fabrics. Or try ebay. I've purchased quite a few from there.
I've made quite a few bags with a ribbon stripe like that and I have done exactly what you said...sew the bottom to the top and then put your ribbon over the seam and top stitch along the top and bottom edges of the ribbon. I usually measure down from the top of the bag as I'm pinning on the ribbon to make sure I get it straight. Here is one that I have made like that: