As to getting longer teeth, I'd fashion some out of a piece of steel. Find someone with a plasma cutter and that job should not be too hard to do. Quicker than a hand hack saw and a file, but that would work too.
What length bar do you have?
I've kept my single set of bucking teeth on my MS361, and occasionally use them when felling a tree. But they are not necessary for the reasons given. On occasion when bucking a large log (bigger than the 20" bar), I'll help the cut using the teeth. Western big-timber cutters will have more aggressive bucking teeth on longer bar saws.
When felling, I plunge cut after making the notch. Neither cuts of which need the teeth, nor does making the releasing back-cut. It is the Game-of-logging technique taught for best and safest felling control of the tree.