Don't use gaffer tape it's messy.

There's a stall holder at the UK camera fairs I go to with a box of replacement bellows, actually he's the organiser. These will all be ex Custom (formerly Camera) Bellows so OEM and they are inexpensive.

The bellows are held in place by the shtter usually so removing the lens/shutter assembly remove the bellows from the front, they are glued in place at the rear so getting them off without damage will be tricky.

Personall I'd get some invisible mend cloth sold for repairing suits etc, very thin with a self adhesive backing and repair from the inside then a layer on the outside then use black acrylic paint to touch up the outside. I've restored badly damaged bellows that way, the make I used to buy is no longer made but it was light-tight which was a big bonus.

Ian