I had exactly the same problem and I bought a pair from Franzose and they fit a treat (as expected) but they are basically just Valeo V28 (280mm or 11" long) and although I'd ordered a load of stuff so didn't mind the few quid extra, if they were all I needed, I'd try more locally first. They are also the type listed for later Classic Minis and widely available from various online suppliers (including a few on Ebay) and probably from your local motor factors; in fact I would also take a look at other brands which are listed for the later ('90s onwards) Classic Mini with the black wipers (earlier Minis had 10" blades).
Funnily (or probably not) the plastic "ends" I had on my arms were identical to the ones in your photos and I simply could shift them by manual means (you get nice new ones, not identical but new ones, with the wipers) and they were too narrow anyway so in the end I very carefully snipped them off with a pair of wrire cutters and within a few minutes I had them fitted. I haven't actually tried them yet but at least they are now not torn, hard and wobbly like the last ones. Good luck. Mark B.