Not traditional, but I've built several reproduction Colt cases using a flocking compound sold by Woodcraft and some others. It is very durable and can be made so that it looks just like felt. All you need to do is strip your old interior and glue in the partitions where you want them. The flocking process starts by painting the area you want to cover with a special colored adhesive and when finished you spray the flocking fibers into the painted area with a special flocking gun. Let the whole thing dry for 24 hours and than use air to remove the excess fibers.
The whole flocking gun setup is cheaper than a couple yards of wool felt (if you can find it) and the supplies will do a couple cases. If you try it, I think you would like it.
