Making these is a tedious process. You need a grid that has 1 x 1px squares. Then you draw your letters a using 1 pixel circle brush using the pencil tool to fill in the grid squares. I'm pretty sure you can't find a font that will work for doing this.
To start you need to draw just the white inside part of the letter.
Make a new layer, change the color to black and draw the black around the letter. Do not merge the layers.
Lock the transparency on the white layer. Next count the number of letters and duplicate the white layer that many times. You will have one more white layer than the number of letters and that is what you need.
Here is a screenshot of the zoomed image of the word GIMP that I drew one pixel at a time. The white area is on a separate layer from the black area. The green lines are the grid.
Be sure you are zoomed in far enough to be able to see your image well. I locked the transparency on the white layers and used the rectangle select tool to fill the letters with green. The bottom layer remains all white, and when the top layer is filled with green you are finished coloring your letters.
Here is a zoomed in image of each layer and how it is colored in sequence. The image includes the black border that will surround the other letters.
Here is a finished animation of it all. I can't anticipate what more you might need so please feel free to ask questions.