A Brother label maker can be had at any big-box office supply store. It prints labels from 1/4" wide to 3/4" on a variety of different colors, including clear, with black or white letters. Buying the machine and an assortment of tape cartridges can be quite expensive, so if you have only a limited number of things to label, borrowing one might be more cost-effective. You can probably get pre-printed labels, but they are never quite exactly what you need, and they also lack the correct labels for those oh-so-important unused breakers. Interocitor? Photon Torpedoes?
It also makes passable labels for your line clutches and the larger size tape is even good for discreet "lift here" labels under the rails for sling placement.