Got your PM buddy
unfortunately the custom cases I use for my collection are only obtainable from within the UK so don't think it would help you very much...sorry
If i'm being totally honest, as nice as most collectibles look inside a glass or Perspex case, I wont be using cases on any of my LSF's...instead i'll be focusing on what the Doom base will be placed on which will be some kind of rectangular plinths similar to what Sideshow were using for their LSF display
I'd imagine that these kind of plinths would be fairly easy to make to help save cost or alternatively, one could improvise and use some kind of similar shaped piece of table or furniture unit and cover it up with a black sheet to recreate the same affect