Yes, I had a similar cracking ( to Rax's photos) failure of a similar unobtainable knob on the vert V/div of a Tek 466.
That was about 3 years ago. I think it was caused by stiff detents.
I clamped and glued it, I recall with JB Weld ( 2 part epoxy)
I did not try to close up the crack completely, thinking that might cause another crack.
So far it is holding.
Also the detents on one probe AC-Gnd-DC switch got so stiff I removed them, thinking that switch would break.
The Tek 466 was purchased damaged about 15 years ago with both the B and A trigger concentric controls with fractured knobs and bent pot shafts.
( They are protruding at the right edge of the panel)
Not finding replacements, I looked at earlier models parts photos (eg Sphere Research in Canada, they have Tek and HP parts)
I purchased some older model 10 k pots with similar inner concentric switches , along with older model knobs.
Turned bushes and nuts out of brass on the lathe and purchased a tap to thread the nuts.
I also turned replacements for the rear feet on this 'scope ( combo case clamp, rear stand and cord wrap)
out of Al. -but without the cord grip grooves.
The repairs are functional but not original, scope is working OK.