If you want something a little more sturdy than the standard plastic
DSLR body cap that came with your DSLR, then you may want to have a look
at the LockCircle.
The LockCircle is an aluminum DSLR cap for your camera body and it has been machined from solid billet aluminum, the video below shows how they are made.
It certainly looks very well made from the video and would definitely
be an improvement over the standard plastic cap, although they aren’t
cheap as it will set you back $100, you can find out more information
over at LockCircle.