Ah memories of cannibalizing old TV sets. If you go with a used one, make sure you get a linear taper and not an audio (logarithmic) taper pot.
OK, if I understand the potentiometer conundrum, the Curtis uses a 0 - 5K ohm variable resistor (the center and one end of a pot.), and the forklift controller came with a ~23K ohm pot. From your photos, it looks like a common part:
a single-turn, linear-taper, 1/4" shaft carbon potentiometer rated at 1 Watt (without a built-in switch I assume). Don't put an underrated part in or you might smoke pot .
Anyway, if you can't get the exact length shaft, you can always go over-size and cut it to fit (usu. aluminum).
So, which controller are you going to be using?
Reality is merely an illusion, albeit a very persistent one. - Albert Einstein
The forklift pot is interesting. With a jumper wire (short) connected between the 2 ends of the resistor, the 0-23k pot acts as a 0-6-0 k pot - meaning resistance is highest with the wiper centered between the 2 ends and drops as you turn it either way from center.