Trapeze wire stopper knot

If you want a short trapeze wire and a long pulley block system for maximum height adjustment you run the risk of having an excess of roap when set to a short setting and this can tangle in your spinnaker sheets etc.  

One solution is to have a single piece of rope between the adjustable pulley system and the wire. This single piece of rope can be adjusted to the days wind strength by a stopper knot or slip knot, and if the wind gets heavier can be lengthened between races or shortened if the wind drops. Whilst sailing, the instant / fine adjustment is still the pulley system. 

Rather than just use a figure of eight knot or tieing a slip knot, there is a plastic figure of eight that can have the rope tied around it that makes subsequent adjustment easier by cold hands etc. An example is on February Yachts and Yachting page 39 in an advert for something different (wichard by proboat just underneath the trapeze handle). Does anyone know what these are called or where you get them ? Are there better solutions or what knot is best to use ?

Cheers

Mike