This is my throw lever for the excellent quality/design/value Vortex Diamondback HP 3-12x42. Should very likely work perfectly with the two other models in the Diamondback HP line: the 2-7x32 (discontinued) and 4-16x42 (what a great scope), but has not been tested as I don't have those scopes. If you try it and it works out, I'd love to hear about it in the comments. I'll be tweaking this design to work for my other scopes which include a few Vortex, Burris and Primary Arms models. "Follow" my profile if you want to receive a notice when I post new parts.
Hardware is a #6 nut/washer/screw (1/2" length), and I greatly prefer to use a nylon-insert locknut rather than an ordinary nut. An ordinary nut will fit deeper than flush into the hex-inlet, and a locking-nylon nut will stick out just a bit, not enough to be annoying. These bits are very common and easily purchased at any hardware or home improvement store. I like the stainless versions: same price you just get fewer pieces in the package.
An easy hint for installing the hardware - the hexagonal nut recess is very tight, and is most easily "pulled" down into place by the screw. A longer screw on hand (say 3/4") can be helpful for this task, though with a little practice I'm able to use the 1/2" screw just barely, to grab the nut and pull it all the way down into the hex recess.
Also, depending on your printer calibration, you may need to trim a tiny bit of plastic from the interior of the ring just where it meets the printer bed/surface. My own printer is setup to mash the first layer pretty hard down onto the glass, so this creates a small lip that needs to be trimmed off to allow the part to slip over the rear of the scope. Easily done with my pocket knife or an X-acto. (watch those fingers!)