Label Maker v1.0 by Michael Moore and adapted by Phil Degelia (original by S.P. Tulk) is an excellent disk label printer that should work with most Commodore compatible dot matrix printers, but designed in particular for the Gemini 10x/15.

This program supports five lines of text and has tons of options for printing style and borders.  You can also save labels that you use quite often by adding them to a specific place in the code.