I would appreciate some suggested sources for gears in a rack and worm configuration.

The requirements of the gears could be described as Hobby. I am working on an idea for an adjuster and would like to drive the adjustment with a worm type setup. Brass / steel sounds good, but I think plastic would even work. Just getting started so I don't have a lot of particulars. I imagine the worm being driven with a ball end hex key - say 3/16 to 1/4 size. The frequency of use would be a few turns per year.

Thanks in advance. Daen