Dear fellows,
thank you very much for your support! As I do live in europe, and I am used to metric tools, the american seizes do confuse me. Sorry for that.
I got a 4 mm spanner, which fits perfect. Now I just have to wait for a 7/64 allen wrench, which will complete my toolset for Alembic.
I took a little picture of the tools.
Thank you again for your help!
Best regards from Germany,
Christoph