A crescent wrench will work, but if you plan to torque it down to spec. when you re-assemble, you'll need the socket anyways. Crescent wrenches are notorious for chewing things up, too. Sorry, I don't recall the size off-hand, but I think I got the socket at AutoZone or Sears.
I didn't use the "Suzuki special tool" for the steering stem nut underneath the triple. They provide a torque spec. for it, but it's just a starting point. It really needs to be adjusted so that the steering is weighted correctly (200-500g for my 1st gen, as measured from the handgrip, IIRC).
You'll laugh (or cringe) when I tell you how I adjusted mine: channel-lock pliers. I used a rag to protect the nut and adjusted the pliers so they gripped firmly without slipping. Worked like a charm.