I had this idea in my head for a while, and decided to do something about it this morning.
EDIT: Mods/Admins I realize this topic may be more appropriate in Equipment/Others. Please move if necessary, sorry about that.
-3/8" webbing (I had this leftover from a shoulder strap for a Lowepro PnS case.)
-Various tools, punch (or a nail if you don't have one), rivet tool (~$18 from and DIY shop)
-1/8" / 3/8" blind rivets + metal washers
-Wide shoulder strap from any luggage or shoulder bag
-Cut 2 segments of the thin strap, each about 15cm long.
-Use lighter to fuse the ends to prevent fraying.
-Figure out where to punch holes (hard to describe, refer to photos below).
-Punch the holes using whatever tools you have handy. I used pliers, hammer, punch, and awl to expand the holes.
-Push the rivet through the hole, place a washer on the other end.
-Use the rivet tool to tighten the rivet.
Please excuse the sloppy photos, for illustration purposes only.
Here's the top attachment point.
The other attachment point is on the 2nd segment of one of the legs. As you can see, the rivet goes through 4 layers of webbing, and a washer on the other side.
Folded up, ready to go. I would clip another shorter strap around all 3 legs somewhere in the middle to keep them from opening up on the go (if your leg joints are not tight enough).
Fully extended. Because the attachment points can slide up and down on the leg and the center column, they can accommodate any tripod configuration. You never have to remove the shoulder strap!
Hope that gave you some good ideas. Happy shooting