First at all: 19 is a lot.
How did it happen? What do you have? Text file? How are you sure the rest of characters are correctly recovered? Do you miss beginning or end?
If there would be less characters, but maybe randomly distributed, I would say my WifSolver could help: https://github.com/PawelGorny/WifSolver
Because you have many characters missing, if you lost the beginning you may use much faster version, build for GPU: https://github.com/PawelGorny/WifSolverCuda
That program would not work if you have your characters missing at the end. Then you should try to convert problem into simple brute-force tool like BitCrack.
There is also 4th option. If you know public key (address has outgoing transaction) we may use Kangaroo, normal or modified for solving WIFs (https://github.com/PawelGorny/Kangaroo)
Let me know if you need hep with any of tools, we will try to find the best approach. But honestly speaking, as you sad you are sure 19 characters are missing, the only chance to restore it in reasonable time is to have public key and attack with Kangaroo.