I just checked the data sheet and Pomona do in fact use RG58.
Yes, I'am afraid so. I doubt you will be able to find one with a much nicer cable. The reason I suggested replacing the whole cable is that:
- "safety"-type connectors are often molded to the cable, hand-assembly-type variants are not necessarily readily available
- if you could get one for hand-assembly, it might well be more expensive than a cable assembly and you probably need a crimping tool as well.
I suppose you could put an insulated BNC on the existing cable (or on some other coax you like better) instead and use it with a suitable BNC to dual banana adapter (Fluke PM9081, Stäubli 67.9537-21...). Those are available as a crimp version (Pomona 73104).