Baa, Haw, haw, haw !!
I thought so. Old Zonie found you.
Getting back to those locks, I'm sorry to see that Royal Enfield changed them from the all metal ones they used to use.
Although the locking finger was made from die cast pot metal, I've never had a problem with mine.
I have heard a few tails of woe about some folks loosing their sidecovers though.
I don't know if it was because they didn't really get the covers locked or the old locks broke.
If I were you, I'd try the ones from Hitchcock although I'm sure the key would not match the one you have now.
As for finishing your blunderbuss kit, those questions and thoughts are more suited for the other forum than this one.
Zonie (Baa, haw, haw, haw).