I was able to get help from my state's disability office. It was a little difficult at first because my case worker wanted to know why I wanted to get tested when I looked fine, and communicated fairly normally. They also wanted to know what good it would do to get me evaluated at my age. I was 29 at the time, so I explained to them how I wanted to get accommodations at work and school; I also explained to them about my issues in attention, memory, learning and executive function. After talking with them about my issues I was set up for a neuropsychological evaluation, which was split into two five-hour sessions. I was able to get for it for free, because I didn't have much income, so you might still have to pay for it even if you get it through the state. You can get evaluated by finding a neuropsychologist in you local area. If you are in a major metro area, you might try contacting the local medical school if you have one nearby. Some medical schools have an autism clinic, where they will provide evaluations, I don't know about the cost though.