You could just spring the rear triangle open 4mm every time you put the wheel on. The article says: "Ideally, the frame spacing should exactly match the hub spacing. This makes for easiest wheel replacement. In practice, however, there's a fair amount of latitude in fit. In fact, when the first 130 mm 8-speed hubs were introduced, they had locknuts with beveled sides, so that you could "spring" apart the rear triangle of a frame made for the then-standard 126 mm spacing."
It all depends how precious the frame is and if you would rather hunt for a 126mm OLN wheel.
Check out sheldon's article on this: http://sheldonbrown.com/frame-spacing.html
You could just spring the rear triangle open 4mm every time you put the wheel on. The article says: "Ideally, the frame spacing should exactly match the hub spacing. This makes for easiest wheel replacement. In practice, however, there's a fair amount of latitude in fit. In fact, when the first 130 mm 8-speed hubs were introduced, they had locknuts with beveled sides, so that you could "spring" apart the rear triangle of a frame made for the then-standard 126 mm spacing."
It all depends how precious the frame is and if you would rather hunt for a 126mm OLN wheel.