I don't have suggestions for places, but I do have some suggestions. My son has mild dyslexia, I just know this due to being an elementary teacher, my husband also has mild dyslexia. For the education realm they do not consider a child to have dyslexia or the need to test for it until they are in 3rd to 4th grade. They do this because most children reverse their numbers and letters.
That being said, here are couple tests you can have him do.. first make a list of simple words that are easily turned around. For example, no and on, of, not, etc. Have him recite these words to you. Also make a list of letters and numbers 6,9, 3, E, b, d, p, q, g etc. and have him recite those to you as well. If he mixes these up you are pretty sure that he will have dyslexia.
Now, a way to help him is to have him do visualization. What you do is have him take a letter, a word, a number, etc. and have him write and say the word in the air. Make it big in the air and have him either say the word sounding it out, or the letter by saying and sounding it out, or the number.
For reading you can get either a ruler that highlights a line of words as he reads, or just use a simple ruler, depends on how hard he struggles. Have him underline just that row of words and have him read. This will help his brain to focus on just 1 line or reading and will also help him to get the words correctly.