One detail that you have not mentioned, is the pot log (A) or lin (B)?
If you do not succeed on this mission there are at least 4 possible ways out of the situation (probably more that I am not aware of). In order of ease IMO:
1. Is a split shaft version available. Screw on knob will work on split shaft. You can always file a flat onto the split shaft if you want.
2. Non PCB mount pots of your desired size are available. Use flying leads to the pcb board and solder these to the pot. The tags on the pot can be bent / moved / cut down as required.
3 Re-use the three pcb mount legs (solder pins) on the 'duff' pot. leave them soldered into the pcb, snip them through. Use a non pcb pot, adjust the solder tags so they make good physical contact with previous pcb pins. Solder them up. You might want to make a temporary jig to hold the pots in the correct vertical plane so that it is soldered at correct height.
4. The difficult one (which I have done in desperation). Obtain two pots, same make with the pressed folded tabs holding them together (CTS). One with the correct 100K value, centre detent etc. The other one values do not matter but must be the right angle pcb mount. Dismantle the two pots and transfer the correct internals to the pcb mount, reassemble.