Hi they are called Stauff clamps, had some from when I worked for an engineering company. They are normally used to hold industrial pipework.
This is their website in the USA http://www.stauffusa.com/
You do sometimes see them on Ebay as well but normally quite pricey.
They are excellent quality for holding pipework but at a price!
I have been looking at the wiring, its got a 2 pin plug so I have wired up the rear light bulbs to the tail light and they work fine, the yellow wires for the 21w stop lamps have been cut off very short (at manufacture I assume), is this normal?
Don't know if this was done on certain orders to reduce battery drain?