I recently purchased some on Amazon about 1-2 months ago. I hadn't heard of it being discontinued...hopefully that isn't the case. But a quick search on Amazon finds nothing now.
Here's the link to Kordon's website. There's a phone number to customer services you can call to maybe get an explanation or an idea where to find their product...maybe they will sell it to you directly.
There are various non-aquarium methylene blue products for sale on EBay. Just be sure that the grade is higher than technical, and beware that some solutions are ethanol based, which of course won’t work.
Jay