No kit available for that particular conversion, you'll need a g23 upper.
If you own a G23 or 32, you can convert it to shoot the following:
The reason the G19 cannot be converted is becaose the hole in the slide that accfpets the barrel is too small to accept the larger 357 or .40 barrels.
The right thing to do,IMO, is to sell the G19 and get a G23. :supergrin: