Hi group,
Here is a version of the HP Agilent Keysight 0370-3238 knob. This knob fits the 6mm D-shaped shafts found on the following power supplies:
6541A, 6542A, 6543A, 6544A, 6545A, 6551A, 6552A, 6553A, 6554A, 6555A, 6571A, 6572A, 6573A, 6574A, 6575A,
6632B, 66332A, 6633B, 6634B, 6641A, 6642A, 6643A, 6644A, 6645A, 6651A, 6652A, 6653A, 6654A, 6655A
6671A, 6672A, 6673A, 6674A, 6675A,
6680A, 6681A, 6682A, 6683A, 6684A,
6811A, 6811B, 6812A, 6812B, 6813A, 6813B, 6834B, 6841A, 6842A,
85108L
E3784A, E4350B, E4351B, E4356A, E6187A, E6188A, E6189A, E6238A, E6242A, E6248A
The part was created used Fusion 360:


The knobs installed on an Agilent 6811B AC Source:

Regards,
Jay_Diddy_B