There is an identical thread running over at CPF.
http://www.candlepowerforums.com/vb/showthread.php?t=100031

TR

QUOTE: I tried doing this, it didn't give good results...
If you want the lanyard to be flexible even at the junction point, you need to take a smaller piece of heat shrink tubing. In this case, it's too easy to pull the two ends apart."

Bee,
Thanks for the feedback. What you are saying makes sense.

I think the only other heat-shrink technique may be to run both ends of the lanyard through the same end of a wider segment of heat-shrink tubing. That puts the heat shrink in the same configuration as a knot at the end of the lanyard cord. The lanyard would remain flexible, while the heat shrink tubing could remain short. The trick here is having enough friction to keep the ends from sliding out prematurely. Only one way to be sure... test it. I'll see if I have any spare heat shrink of the proper diameter to accept two ends of cord, side by side, yet shrink down enough for a snug fit.

Another option may be one or more small O rings used in the same configuration, as a knot replacement, lanyard ends side by side.

I'll post back if I can dig up the proper components.

TR

I just remembered this, for what it's worth.

A friend of mine showed me a trick that he'd learned when was last on leave, where he guts a chunk of paracord, and runs break away chain through it, for his dog tags. That, run through a standard split ring on the whistles?

I know, it looses most of it's strength, but it's still strong enough for most things.