The tricky part with this is that Superman will be copyright, so I doubt you'll find a pattern at all. I even had a quick look for a more generic superhero one you might adapt, but no luck. I think the only thing you might find is one meant for speed skating, but a lycra catsuit for a man wouldn't be the easiest thing in the world to get right (though fittings might be fun!)
I think the hire or buy route would be my choice.
SupermanThis link is to Warner Brothers, but I hope you're sitting down when you see the price. I'd imagine people hire these though.
I don't know what you're doing, but you'll also have to watch advertising materials because of copyright. These big corporations don't muck about!
I suppose one final route would be to try to buy the catsuit from a dance shop and then make the rest of it.