I need to take my CFII written, but can't find any information or study guide for the actual CFI Instrument written. Any thoughts?

get the regular instrument rating test prep book from ASA. its almost if not exactly the same test bank. if your gonna take that also take the IGI test which again is almost exactly the same test bank.

the other option would be sheppard air. have heard good things about all their software but never used it myself. they guarantee 90% or your money back. A coworker of mine got an 88% on his ATP and they had the money back in his account the next day

Just study the questions you did for your instrument rating. The CFII test is about 90% the same as the instrument test. I bought the Sheppard Air study guide but if you took the IFR test recently and got a good score on it you should be fine.

You can't go wrong with Sheppard Air

Sheppard Air that sh*t. Same question bank as the Instrument Airplane written.

Sheppard Air is the best bang for your buck. I used them for my II written a few years ago and it went great. A couple days of studying with their program, and scored in the high 90's. Can't go wrong!

If I remember correctly, most of the questions mirror the IR written but there were a handful of unique ones.

+1
Yes do this: for your Ground Instructor Advanced Instrument license.