I thought about it, I'm the kinda guy who would spend more just to get things the way I want them!

It would be an easy job for someone with the skills and a machine shop, I have neither of these

I would just want it made from a good quality steel, not alloy or aluminum. Then I would just have a local gunsmith hot blue it for a few bucks. You would just have to measure the dimensions of the rear sight channel, drill the pin hole in the right spot........and match the height of the rear sight notch to the adjustable sight that's already dialed in. I would gladly pay someone $100 or so to get it done locally, if they felt they could get it done right.
I already test fired it without a rear sight, using the sides of the empty rear sight channel as a sight, and it hits dead on but way low. The windage is right on so the rear sight notch could be centered in the machined sight, using the red insert GP100 front sight I have on there already.
I have always dreamed of having a full lug, fixed sight 6" GP100..........I almost bought a 6" Dan Wesson Model 14 .357 with fixed sights, but I'm not a huge Dan Wesson fan. I had two but sold them both off.