Shy, years ago while I was welcoming the pax onboard at the door, a young lady said to me "Hi, I'm an FA with so-and-so airlines, I'm in seat 1X, and if you need an assisting pax in an emergency, please feel free to call on me".
It was polite, it was colleguial (spelling?) and made me aware of a potentially useful bit of information.
It also gave me an opportunity to upgrade a fellow fly-nut without her putting any pressure on me or asking me directly.
Since then, I have used the very same phrase whenever flying, and it is met with anything from a blank indifferent stare to great entusiasm and an upgrade. And it's all fine by me because I feel that I have done the polite, professional thing.
Maybe you could try something similar and see how you get on?
(boarding is a very hectic phase of 'flight' so be short and to the point)