I've been looking at doing this mod and, after having taken a close look at what's being offered for $500, I'm convinced that this can be done at home with a plasma cutter and MIG for not much outlay.
In my case, I have scraps of 2mm & 3mm sheet lying around so it should be really cheap to do.
I'm thinking it can't be too hard to make some cardboard templates once the spring is out.

Has anyone made their own and have pics they'd like to share?