Check ebay. A few months ago, I found a guy in the UK selling 12 of them at once. I bought four from him at the time. Also, the Kodak B&W Dataguide from the 1960's and 70's had them included in the book, so you could look for one of those real cheap. But you will need to use it with the HT-2 test solution, I don't think using KRST will work the same.