Not sure if this helps you but try:
http://umanitoba.ca/faculties/afs/arborists/index.html
U of Manitoba uses the same ISA textbook with it's own Q/A's, plus online course materials, plus weekly on-line quizzes and a final exam - this can be at UMan in friendly Winnipeg (also great beer, rye bread and pyrogies!) or proctored at a US testing center. You'd be prepared for sure, plus it's accepted if you want to go on an take a TRAQ course afterwards, for example.
Next intake is January 2018! Registration fees are in our bargain basement "Highly Devalued Canadian Dollars" (well not a dollar actually, more like an inflated 75 cent piece with Duty/ All Manner of Brokerage Fees/ PST/ GST and an assault on the senses by the banks for the currency exchange rate they apply - no wait, I digress - this is for equipment purchases made in the US!)
I think there are also some prep courses available in the US through some of the ISA Chapters too - these you'd have to attend in class that I've seen.
Cheers