For what it's worth: Bandcamp has a shopping cart feature while still forcing you to pay for every band separately. When you check out, instead of making one big payment with Paypal, you get repeatedly sent to Paypal to make a smaller payment to different sellers until you've payed for everything in your cart.
While making lots of small payments instead of a big one seems to defeat the purpose of a shopping cart, it doesn't really:
- Multiple purchases by the same seller are grouped as one payment.
- You can add things that you think you want to your shopping cart and remove them again when you change your mind later, so long as you do it before checking out.
- You can see how much money you're about to spend as a lump sum, and remove things from your shopping cart when you're going over budget.
- The acts of choosing what to buy and paying for it are separated. Your shopping isn't constantly interrupted by paying.