Surprised that nobody has mentioned the Telex/Jeppeson type, A5, -light/strong Aluminium with strong clips top and bottom and a good, wide elastic leg strap.
Originally designed for the US Navy and Air Force, this is a good bit of kit- only drawback is it might be a bit pricey now.
I got mine for a fiver at Shoreham Aerojumble years ago!
Seasons Greetings,
Sleeve.
P.S. Forgot to mention, it also comes with a clip-on light at the top
and this addition incorporates an easily accessible pen/pencil clip.
If the clip-on is removed , the slots can be used for attaching a Terry clip for your stopwatch. Best bit - won't fall off when you're inverted in a Chippy !