I use 2' long sticks with a 2' wide top string. I used Rayon mop head string but you can use anything available to you. The top string has double the amount of strands as the bottom (4:2 or 2:1)
You can use a utility knife or...
....or a 1/2" half-round file or to cut the groove for the string.
Make a grove near the tip with a razor knife, file, hacksaw or anything handy. Tie a durable synthetic string around the tip. (I melt the ends of the string with a Bic lighter to make the knot secure) and maybe even a spot of superglue..
This is what you want.
Equipment needed: 2 sticks, some string and a straw. Won't twist or tangle onto itself even though there are no swivels or clips. These are not intended to be pro caliber gear. They are simple, cheap and easy to build. In an interactive event these are some of what I hand out for the kids to enjoy and they make great gifts or rewards at no great expense.
This approx. length string is necessary as a leader so the tri string won't twist. The straw piece is necessary so the two ends at the tip of the sticks do not tangle with each other when you dip your tri string.
BEFORE tying the string the the end of the stick I slide a piece of regular drinking straw over the end of the tri string and out of the way (as shown)
I carry a whole bundle of these to my outdoor interactive events.
An option is to add a tiny bit of weight to the bottom of the tri string--here I used a small metal washer.