I also emailed Michael Grinter, who also uses the box clasp I like. Here is "his" reply, which actually came from his wife helen, who makes his boxes.
"Hello Jay,
No problem about asking where we get our sliding box catches from. They are made by a company called Gebr. Maissenbacher who are based in Germany. However, we don’t source them from there but from a company called Ivor Spry in London. I haven’t ordered any since late last year and in the meantime the company has changed hands so I can’t really comment on their service as from now but in the past it has been excellent. I usually order the catches in batches of 100 so I’m not sure what the minimum order would be if any – best to contact them directly.
Here are the details for you..
Mike King
Director
Ivor Spry and Co
Knight’s Hill Square
London SE270HH
Ph. 020 8761 1813
Fax 020 8761 8796
E-mail
sales@spry.co.uk
The catches come in left handed and right handed options and are really very good quality and I don’t think particularly expensive for what they are. There may be a company in US that carries the range, but I didn’t find any when I was searching for them a few years ago. I got the contact for the catches from Andrew Crawford’s wonderful fine-boxes website.
Happy hunting and good luck.
Regards Helen (Michael’s wife and also the boxmaker)
P.S. Forgot to mention that Ivor Spry have a website the address of which is
www.spry.co.uk. It’s not particularly detailed but they sent me a catalogue which is full of all sorts of other handy items like small screws and hinges. Highly recommended!"
Best,
Jay
...here you 
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