Replacement pads for Dura Ace 7400 calipers

[Steve in SLO]

Looking for some replacement pads for the above calipers, and would prefer to find Koolstop fitment if possible. It looks like the C89 series is the closest fit. Has anyone tried these or have other bright ideas? I would like to keep the stock pad holders, if possible, and would prefer to avoid Shimano direct replacements, since their age would be in question.
Thanks!