...but I've never tried it myself. woodcraft.com has brazing jigs, or you can come up with your own.
The biggest part of the battle is getting the two ends cut and jigged perfectly square so the blade weld lasts a while. The second trick is in Annealing the weld after you're done, so it isn't brittle and doesn't snap again in minutes.
If you can find the regular resistance welder they usually mount to the side of the saw itself, that's usually better. The Simonds looks like a beauty, has multiple heat settings and an anneal timer all built in - and I'll bet they are a bloody fortune.
But if it gets used a lot at a commercial shop, and it will if you usually go through a lot of pre-made blades that could easily be welded and keep going, the savings will pay for the welder real fast. You can buy a 100' roll of continuous blade stock for the cost of a dozen pre-made ones - and you can make the odd lengths and tooth-count ones yourself.
Sometimes you need to make an INTERNAL cut on a workpiece - so you drill a starting hole, thread the band through the workpiece and weld it in place, mount it on the saw with the work on the table, make your cut, then cut the band to get it off again.