Gary at Martin Model & Pattern here. I have about 200 die files for sale. The photos and drawing posted by John show the shapes and a good representation of the files available. They used to be had for $5 a piece and now they are mostly unavailable under $10. I sell mine for $15 each for the new ones, with $8 for shipping. If you order a larger quantity of 8 or more, I will ship for free. Overseas I would need to know your address to give you a quote for shipping.
I have very few of the small 3-1/2" long ones left, which were perfect for my Die Filer Casting Kit. Most of the ones available are in the 5-1/2" range up to 8" long. There are quite a few that are very small in cross section of various styles that require an overarm. I have a large number (dozens) of 5/8" wide half rounds, as well as 3/8" square, both 8" long. Most all others I just have less than a half dozen, a majority just one or two, so it doesn't work for me to list all I have as that one may be gone tomorrow. I reccommend emailing me with your specific wants, and I will gather those I have together and send you a couple of photos from which you are able to choose .
I am reluctant to post here as I do not want to be on anyones bad side for advertising, but I truely just would like to help people find what they need. I make my living as an industrial patternmaker, but as a former public school shop teacher wanting to keep all the trades alive, I enjoy the hobbly just as all of you.