Amazon has it listed too, with a couple good reviews, but I only saw first grade
Here's an
Amazon search showing results up to grade 6. I'm not sure if any exist beyond that, but if so I haven't seen them.
kiwi, I think it depends on how that reading age of 13 was assessed. If it's something like a quickie assessment tool like the DORA test, he might well get benefit out of something less than the 6th grade one. If your child has all the reading skills of a typical 13 year old, I might just spring for the 6th grade one and hope for the best. In fact that's probably a good idea to start off; they're not very expensive and if it's a little above the optimal range for your son (which might be unlikely, I have no way of knowing) you can keep it on the shelf until he's ready, while you order other ones; if it's beneath his level you can return it and search for something else.
