What are some other ways to express uncertainty or lack of knowledge without using phrases like 'I'm not sure' or 'I don't know'?

I’m not your best source for information on that point.

I defer to what other people may tell you on that point.

It would be unfair to you if I made a guess about that.

That’s an area where I have always felt I need to know more.

You want to hear from people who have better information than mine.

I’ve wondered about that for a long time without figuring out the answer.