I've got an HP supply from the mid-70's and it uses standard banana jacks that look just like those. In fact, pretty much all HP gear used the same jacks through the 70's, 80's and 90's.
What do you mean when you say it doesn't fit? Is it too loose or too short?
I've found a lot of older equipment used banana jacks that seem too short for modern banana plugs (that is, when a lead is plugged in it doesn't go all the way and there's generally some of the metal plug exposed).
I tend to just replace these types of jacks with new ones. For supplies with rear screw terminal access, I'll use the non-binding post style jacks (because they don't extend the leads out as much and the plug is more secure, which is important when you stack cables like I often do).
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