Why don't you make one that suits you needs. Just draw one in the drawing, select and right click on the sketch and from the list select make block. After you finish creating block, right click on the block and from the list select add to library. Now you use it as and when required.
Yes, I know how to make a block. I was just wondering if someone had one that would automaticly scale to the right size diameter dowel on insert. I know you can scale blocks also!