I would bite the bullet and go with option A). The other two options are a lot more work.
I would be surprised to find some sort of stop-leak for residential plumbing, because whatever doesn't stick to your leak is gonna stick somewhere downstream, and Murphy's law says it'll be in the worst possible spot.
How long has this tub been in place? If it's got PVC pipes for DVW, I'd think maybe a seal at the tub itself is more likely to have failed than something in the pipes.