I was at a neighbor's yard sale last weekend, and found a "Martha Stewart Collection" bathroom tissue box cover for $0.25
I had a piece of piano hinge left over in a junk drawer, and cut it to fit the box.
Now I had an excuse to go to the Hardware Store! (One of my favorite pass-times) I got a cabinet door magnet and nuts & bolts to assemble everything so I could mount it to the bottom of the "Child's Bunk" shelf that I use for soft-goods storage.
Hang box by a hinge. Add cabinet magnet to back side.
Push tissue box in from the back.
Just reach up and grab a tissue.
Some people put things on top of shelves. I use the bottom.