I use a product called Dynamite 18-6-8 (green) which also has micronutrients. I use for all my ferns - I purchased ratty looking ferns from Walmart last year, used some of this fertilizer and the lush new growth was awesome. I think I've seen the product at Walmart, Hawks Nursery, and Minor's Garden Center.

I know this isn't the product you are asking about, but an alternative if you can't find what you are looking for. Good luck.