There used to be ads in the cycling mags for tub repairs – if anyone knows how to do it it’d be them – if they’re still at it.
My uncle used to do this. Since then he’s had proper jobs, retired, turned 70, and unfortunately started to get a bit of Alzheimer’s.
Tubs used to be far, far better than clinchers. Nowadays, clinchers are competitive particularly on road where a lower pressure can dampen out the chatter a bit, giving better real world rolling and negating the ability to put 180+psi in your tubs. Some big races are being won by folk running tubeless too.
For now they still have a place on track or very smooth road, IMHO, and perhaps fro CX where you can conversely get away with lower pressure without pinch flats.