In reply to FunesTheMemorious:
Thanks all for the responses. To be clear I wouldn't be wearing the chalk bag with my phone in it, agreed that is not a good idea.
I just wanted one I could stick my phone in on the floor when on a circuit board for example. A chalk bucket felt like overkill so in effect I'm just looking for a large chalk bag that can double up, I'd take the phone and brush out if I was strapping it on.
It looks like the Mammut one fits the bill perfectly, thank you.