Jumpy needle

Hi

I have a Winter vario, which is works OK, but I find the indication a little
jumpy...
The system is not leaking, but I'd just like to have slightly less "gust"
jumps and a smoother move of the needle.

In my ASW20 there used to be a restriction in the tubing and apparently it
did the job pretty well with the same type of vario.
Indeed, restriction in the tubing seems to be the way to go:
http://www.sagevariometers.com/sagehint.htm

But then my quesion is:
Where can I find a restriction (preferably France, or Europe) ?
Making one would be an alternative, but very tedious I guess (what's the
correct length ? diameter of the capillary, ...)

Has anyone successfully applied this solution and got a better/smoother
reading ?

Thanks for the info,
Ludovic