Nothing you can do about it aside from lying about your age... which i wouldn't recommend.
If they think you're too old, that's their decision.
find the ones who don't mind that you're 40.
BTW: If you're balding, have a beer gut and have never been married then yeah, you are too old.
On the other hand, if you've kept in shape and don't "look" 40 then I don't think age really matters. I'm 27 and I've dated 38 yr olds and 19yr olds at the same time. Age REALLY doesn't matter, as long as you're "Mr. Current Affairs" and know what's up. Don't get caught in the generation gap. You gotta keep on top of things as far as style, fashion and pop culture is concerned.
Be a modern man and no one will care..... or at least they will care very little.
I find it funny that 35 yr olds would be shooting you down. Men age better than women and by the time she's 40, things will look alot worse for her, than you.