I bought some NOS ones from e bay last year for about £12, but they are the motor bike ones, one is a bit bigger to go over the throttle sleeve, I wrapped a couple of layers of sticky back plastic around the bars on that side and its fine.
The only difference I can see between those and my old ones is the bar side of the flange has a cog molded into it.
Still has the mushroom on the end and still feel brill in your hands!
Mark M