Bead jack, as other folks suggested. I have a Kool Stop bead jack at home. It does fit my jersey pocket, but it's a bit bulky and I might get a VAR or Crank Bros tool for the road.

In a pinch some hard, smooth plastic tire levers with wide spoons can do the trick. But I have to be very careful to avoid nicking the tube. I've had to redo a tire once when I nicked a fresh hole right after patching another. Annoying but that's the risk of using a makeshift tool.

Also, after the first couple of times hoisting a tight tire over the rim, some rubber will be abraded off the bead, just enough to make it easier the next time. I've noticed this with the tight fitting Schwalbe One V-Guards and Conti Ultra Sport II on my road bike.

Friday I used the Kool Stop bead jack at home to hoist a new set of Conti Contact Sport II tires over the rim. Besides being a snug fit the new rubber is very grippy so there's a lot of friction. But I'm betting it'll ease up next time I need to patch or replace the tire. Meanwhile I'll carry the bead jack with me. Much easier with cold, wet hands outdoors.