Speedball / joplin saddle clamp

[stu76]

I've just got a Maverick Speedball dropper post which works ok but I can't get the clamp to grip my saddle rails properly, no matter how tight I get it. I think it may be the clamp rails are worn.

Does anyone have a clamp or parts off an old post that they don't need?
I believe that the crank Bros joplin post is the same so probably compatible too.

Thanks
Stu