The XK140 EXPLORED drawings are made up from photos I supplied of the original clips on my September 1955 XK140MC OTS. When writing up this page of XK140 EXPLORED I was satisfied that these clips were correct/as fitted to all XK140s despite many restored cars not refitting them, and many unrestored cars being lost. You cannot be 100% certain, but in this case good enough (I think). There is some debate re extent of clips being fitted on all XK120s or not, certainly there are many confirmed examples of clips being originally fitted, but not enough to claim all XK120s were.
And Eric - I am pretty sure you are correct that it was Tadek that made up reproduction clips for his XK120 restoration (that did have original clips), but only a handful of extras of which I also received a couple - but don’t believe this was a project to commercially supply clips. Tadek can comment (if he wants to).
I am not aware of another source of reproduction clips, so maybe this current thread may flush something out.