I have a #2, so I'm not sure if it would fit a #3 rack, but I went to my local ACE Hardware and got a black plastic mortar pan for under $15, perhaps under $10. It is longer than I need for my racks, but as I said, I'm not sure how long #3 racks are. But you could always bring the rack with you, or just measure it. I'm sure Lowes and HD have the mortar pans, too. Otherwise the under-the-bed bins is a good idea.