I suppose you are talking about your '75 or '83 bike. They are both wet drive shafts. Not sure about a '94 bike, it might be dry? But I don't know.
The boot is replaceable and the clamps are also available. Two different sizes for the clamps. The boot has a way to fit correctly. Look at it carefully enough and you will see that one end is round, transmission, and the drive shaft end is square. If the drive shaft bolts have been in place a long time they may actually have washers on them and the washers, or some of them, may be cracked or broken. Replace with the shorter bolts that work with out washers. Disconnect the swing arm from the frame and it will move rear ward enough to get the boot in place. It's nice to have a 27mm socket trimmed enough to fit into the recessed area for the pins lock nut but the tool kit box end wrench will also usually work.