I just wear Scott OTG goggles whenever I am in glasses instead of contacts. The only issue with those is the foam is pretty coarse so you have to oil it for really heavy dust. They don't let enough dust through to bother your eyes. But they will eventually coat the inside of the lens unless you oil the foam.
But all that open foam is also why they don't fog your glasses. Look back at that pictue I posted last page. If they don't fog in those conditions they never will. Dirt cheap and effective.
640E, MXC200, XT200