I have used a piece of sullivan yellow inner pushrod just long enough to exit the cowl 3/8-1/2 inch. If you use a short piece of 2-56 rod inserted into the end of the needle valve and screwed or ca'd into the end of the rod you will have a flexible and light weight needle valve extension. It is flexible enough that I do not even have to remove it to remove the cowl and can be fished back out the small hole when I replace the cowl. The hole in the cowl can be off quite a bit and the flexible extension will still work fine.
Fred