Those 8th street and humbucker shock mounts may be ok for the Studio Projects B1, but I'm not so sure about the B3. Look at that shock mount and then look at your B3, how are you going to get to the switches on the B3 when it's in that shock mount? It looks to me like that shock mount would cover the switches on the B3 so you can't get to them.
I have the Studio Projects LQ-21 spider shock mounts, and they don't look like those shock mounts. The Studio Projects LQ-21 holds the mic by the neck (not the body) and doesn't cover the switches. But the SP LQ-21 shock mount is also plastic (I think).