If you have an old film changing bag laying around you can use some of that for a patch, put it inside with some glue that stays flexible. Maybe not rubber cement, it's high-sulpher, i worry the chemicals in it will degrade the leather bellows, but then again, the bellows are leather. Maybe find some good leather/meterial glue?
OR, if you have a dead 35mm slr camera laying around, or can find one at a thrift store for $5 or so, you can rip it apart and use the cloth shutter material to make a patch. This also leaves you with a nice pile of cool screws and other parts.
LOTS cheaper and easier than replacing the bellows, although that is the best long-term solution. Then again, I fixed a small ikonta a bellows that way a mere 20 years ago and it's still holding up.