These are so easily made from the condensed foam that most of my e-cig materials have inside the shipping box..
Use the appropriate drill bit to match your caliber and drill a hole thru the center of said foam.
Then use a good sharp serrated knife to cut to fit snuggly into your rifle.
I've used this method for my Impact, FX Royale & Boss, and all work to perfection.
FYI - If you happen to have any of the single shot trays that come with the Marauder rifles you can file them down to match your current rifle and they work just as well, if not better.
Just a simple, inexpensive fix to a common need that most people have that want "low mount" scopes that won't accommodate the clips that come with these rifles.