Can I use a 500mA fuse instead of a 315mA fuse?
Order the correct one.   

It will work with a 500mA fuse, but you are putting the circuitry protected by the fuse at some risk due to the extra surge current possible. It's quite possible a component will blow rather than the fuse.
In general putting higher rated fuses in is a bad idea, though this is a smallish current and not too different, in extreme cases putting the wrong fuse in can lead to severe damage and possible fire.

So, while the fire or even the severe damage is extremely unlikely in this case, it's worth the wait to order a correctly rated fuse rather than put the wrong one in.