I'm going to attempt to give you some basic instructions to make one of your own, if you find yourself so inclined. Unfortunately, I had this brainwave 3/4 of the way through making the second one, so of course I don't have many supporting pictures. But here goes:
Sewing machine (you can hand-sew this but it will take you forever)
Fabric, two colors. I bought three-and-a-half yards of the main color (brown) and three of the accent color (striped) and had enough to make two of these with plenty of fabric left over. Which was good, because I screwed the first one up :-)
Optional but recommended: seam ripper
Because this is going to be holding a lot of weight, I doubled each piece of fabric so that the end result was double sided. So, you will need to cut pieces in the following sizes:
Main color: 2 pieces, 36" by 14". You may need to adjust the length according to the size of your couch or chair arm; my couch arm is a bit overstuffed. The goal is to have it hang over so you can reach the remotes comfortably, and so you can stuff the other, soon-to-be-marble-filled end between the cushions to hold it in place.
Accent color: 2 pieces 11" by 14", 2 pieces 10" by 14".
Lay the two pieces of the main color together with the wrong sides facing each other. Pin them together with a 1" hem folded around all edges and sew. Set aside.
Now, take the 11" pieces and lay them with right sides facing each other, pin together without a foldover hem, and sew around, leaving a four-inch gap on one side. Pull fabric inside-out through hole, so that the right side of the fabric is now on the outside. Fold edges of the gap inside (so that it matches evenly) and sew hole shut (like a pillow, if you're familiar with sewing.)
Follow the same instructions for the 11" pieces for the 10" ones.
Now, here's where it gets a little tricky. Lay the 10" joined piece on top of the 11" joined piece, with the bottom edges lined up. If you left the gap to pull the fabric on one of the long edges, make sure those go on the bottom. The 14" edge is going to be the horizontal edge. Now, sew one vertical line through both pieces, 4" from the left edges, from the bottom to the top of the 10" piece, and another 4" from the right edge, leaving a 4" space in the middle. This forms the beginning of your remote control pockets.
Lay these pieces on top of the main color piece's right side (the one without the hem wrapped over it) with the bottoms matched up. Now that the hems have all been sewn, they should all be approximately the same width. Sew around edge of sides and bottom, leaving top edge of accent piece unsewn to form a large pocket. Make sure you sew over the edges of the 10" piece as well, so that the 10" piece now forms three pockets.
Now, at the opposite end of the main piece, fold approximately 3 1/2" around the back (the side without the pockets) pin, and sew the long edge and one of the sides, leaving one side open. Fill this small pocket with the marbles, and then sew closed. This weighted edge will be tucked between the arm and the cushion, to keep the remote holder securely in place.
Voila! You have hopefully, in spite of my poorly illustrated instructions, managed to create a remote control organizer. Enjoy!