Not too sure of the Mustang bridge, but if it's larger than a Fender J or P bridge, then not very likely.
I've been playing the bridge-n-cover game and haven't found one to even fit my oversized Affinity P bridge yet.
There really are only two different covers like I mentioned: J or P, not including the older '51 P-type of course.
Here's a link for you to see fer yerself:::
Bass Parts Resource: Bass Covers/Ashtrays