Raspberry Pi 2,3 Case

My Pi is overclocked and sometimes shutdown itself because of heating problem.
So I needed a proper case under those conditions,
1) air should travel freely.
2) big fan (50mm) adopter
3) float from the ground
4) webcam adopter (optional)
As far as I know, there's no such thing satisfy everything.

I'm thinking of making fan adopter for 30mm, 40mm fan if there's a request.

No need
1)support structure
2)bolt or nuts (ovbiously for structure itself, need 4 of m3 bolt for 50mm fan)