Try searching for similar ICOs and contacting some of their Advisors and other people who are involved. Send them an email or a message with the same information you would post here under [ANN] and try your best to show your enthusiasm. Send them a whitepaper if you have one. They will give their feedback, which you should probably take into account and fix any of the problems they found in your idea. After that, you are free to ask whether they would be interested in becoming advisors for your project. LinkedIn is a great tool for contacting potential advisors but make sure to check whether the person has enough experience and is qualified enough to advise you on your project.
Thanks for the suggestions, definitely trying them!
I was also actually thinking of sharing the Whitepaper to get feedback first - good for both parties I guess to gauge interest and expertise levels.
We have reserved healthy number of tokens to make it mutually beneficial.