In reply to Will Furnass: To be honest, unless you are using these just for simple strolls on flat, icy paths (i.e. not on the hills) then I would suggest buying a modern pair as these don't look very usable, particularly with loose buckles. Modern crampons (when fitted properly) will be easy to put on, stay attached, prevent snow clogging the points and provide vastly more security than these things can.
These are not climbing crampons really, they are for strolling down an icy pavement. Even 40 years ago Salewa made proper front point crampons which are still quite usable today on general mountaineering, but what you have inherited are no good for climbing at all... sorry!
Needle sports list Grivel and Stubai replacement crampon straps for less than 10 pounds. The Stubai ones have a similar buckle to your existing but the Grivel ones have their double rings which I'd favour.
Of course they should only be reserved for emergencies when winter hillwalking and perhaps glaciated approaches to summer rockclimbs but at least they will stay on with some new straps.
In reply to Will Furnass:
I've just dusted off my old Salewas - these are 'proper' 12 point crampons, and I'm planning to use them with my walking boots (which my Grivels won't fit onto), for the times when I don't want to be tramping around all day in stiff B2s on the off-chance that I might want to wear crampons for 10 minutes.
I seem to be taking bigger boots than when I last wore them, and the straps are now a bit short. Does anyone still sell the French-style ring bindings?
@Timmd: Yep, I'm wanting to invest in some winter boots and full-length crampons soon but would like to keep the in-steps for contingency use. Yes, the straps presently just feed through continuous loops on both sides of the crampons.
@JimmAwelon: Cheers for spotting the spare straps on NS. Can't immediately see how the double-rings would be better than the Stubai buckles but will take your word for it.