Start your own dating service! It's easy. Let's say your name is Nick. Get a t-shirt printed up that extols your service (as a date) in big bold letters: "TIRED OF LOOKING FOR LOVE ONLINE? TRY THE NICK DATING SERVICE!" Under that, hit 'em with your own various unique benefits as a dating partner. Personalize it! That's the whole point - it needs to reflect who you are and what you can actually provide. Talk yourself up a bit! Why should they act on your shirt, as opposed to someone else's? Use the front and back of the shirt, if necessary, to make that case! Then at the bottom (of both sides, naturally): "Sound too good to be true? Call me on it! Here's the digits: (...) ... - ...."
Please note. Don't tuck the shirt in if you expect this to actually work. Only dorks tuck in a t-shirt.
And when she or he calls the number, it's like: "You've reached the Nick Dating Service. Where every date you have is with Nick! Press 1 if you heard about Nick from a friend. Press 2 if you heard about Nick through an advertisement in the paper. Press 3 if you saw one of Nick's tasteful ads on cable access television. Press 4 if you saw Nick walking around in his personalized t-shirt, and called the number. If Nick is standing right in front of you now, press 5."
This would definitely work! Albeit, you'd know the kind of person you're getting would be the kind who would dial up a dating service based on seeing an ad on a t-shirt. Is this the kind of person you'd be interested in? Or would that sort of thing be a 'dealbreaker'?
See, that's what you'd have to ask yourself, before you even get the t-shirt made.