Magnetrons are fairly expensive new, but there is one in every old clapped-out Briggs made since 1982. They rarely fail, so there are literally thousands of them out there on junk engines. They look and fit the same as your old coil did, you just remove the wire to the points since you don't need it any more.
Because there are more Magnetrons than coils out there in the world, chances are you can get a used Magnetron cheaper than a used coil. Of course if you want to you can buy a new coil and fit it, it will work just as well as a Magnetron, but you will have a few extra components that might eventually give trouble. For example, ignition condensers are somewhat prone to failing when they get very old. On your engine the points and condenser are located inside the flywheel, so you have to remove the flywheel to service them - not terribly difficult, but it is a bigger job just to check the points gap than it is to completely replace a Magnetron.
