To make the letters for the new keys I had thought of designing them in Photoshop. If you don't have that, any other photo editing program should do. I recommend the free program GIMP
. I measured the inside of the buttons first which was about 15/32" The maximum numbers of keys was 18 across and there are 6 rows. According to this I opened a new image 11" wide and 4" inches high. Then I drew 15/32" circles in the approximate arrangement of the original keyboard. I also measured the square keys because I wanted to keep them and not just replace them with round buttons. So I drew the exact shape of the square buttons.
Finally after a long search, I found the font I liked and was going to use. ImperatorSmallCaps by Paul Lloyd, available at: Free Fonts
After installing the font I typed the letter, number or text in the approximate location. Each on a separate layer; sorry I don't know much about other programs what you can do there.
Then I went back, edited the layer and nudged the letter in the exact position, likely the center of the circle. This took about 3 evenings of working in Photoshop.
Last step was to find some nice texture and the right color. I decided on an old parchment look, even if you don't see very much of it.
Some keys would be reversed, black on yellow.
After I was satisfied with the result, I copied the image to 1 layer, cut it up in 4" x 6" pieces and sent them to Walgreen's to be developed there. That would look much better than printing them out, costs just 18 cents a piece and I could pick them up 2 hours later.
The pic of the whole layout is the full size png file for those who are interested. Be aware, it is 4.6Mb !!!