40.5mm filter wrench for the Sony PZ 16-50 OSS lens

I recently bought a Sony a6000 camera with its PZ 16-50 OSS 'kit lens'. It is my habit to put a UV filter to protect the front of my lenses but, in this case, the odd-sized 40.5mm filter decided to stick in the camera lens's thread (not an uncommon occurrence with filters). Normally it is easy to get hold of a filter and unscrew it, but in this case the filter is much smaller than the lens body diameter and it proved impossible to get a decent grip.

There are some designs for filter wrench