Even if you managed to get it on there, which I expect would be extremely difficult, remember that you might have a flat and have to remove it and reinstall it by the side of the road under less than ideal conditions. Tubes can be stretched to cover just about any size in a pinch (sorry), but you need to use a tire that's the correct diameter.
Get the right sized 26 by 1 1/4 tyre (EA1) and do not force a 650B on to your rim. I had a case like this and the removal of the smaller tyre required destructive measures and came with a much higher bill than usual because of the time and swearing that was involved. Had the tyre gond fglat on the road the owner would have never been able to remove it with basic tools because getting it on must have required shop grade levers.
What kind of bike are you working on and can you get these tyres there ?
If tyre availability is a problem send me a PM as I have spares in this size.
Tire beads are specifically manufactured with steel wire or Kevlar to be non-stretchable so they don't blow off the rim under pressure.
This bears repeating. Despite being made mostly of rubber and flexible material, the steel bead of the tire is NOT flexible. Its circumference (and therefore diameter) is fixed. I have run into the exact same situation before ("regular" cruiser tire onto a Schwinn rim). You can't do it, no matter how many tire levers you break. The opposite operation, putting a 597 on a 590, is easy, but the tire will not stay when you try to inflate it, no sir.