As another post or two said, if you are a successful trading and making good money, just come up with a great sounding line - financial analyst, private wealth manager, etc etc
You can create your own title and get your own biz cards printed to show them!
And when they ask you to trade some of their money, explain politely that you are not currently accepting new clients, but you'll be more than happy to place them on your wait list. Make sure to also mention the wait list may be years and years down the road.
In summary - they like your title (people love fancy sounding titles), they know what you do and they realize there's no chance you will accept their $ anytime soon.