On 14/12/2020 17:12, Fredxx wrote:
The mirror is approx 400 x 700mm and is 6mm thick with edge bevels that
reduced this to 3mm.

It has no mounting holes and I don't want to drill any.

I can get mirror corner mounts but these are designed for 6+mm glass,
and conscious the mirror will rattle around in them.

Is there a better way?

Suitable thickness polyurethane foam behind to pack the mirror out
slightly and make it secure?