Since we have a lot of home decor fans here, I thought I'd see if anyone has a solution to my problem.

I've recently acquired several pieces of artwork in non-standard sizes, and I need to frame them. There are five of them and they are all different sizes. All are rectangular and flat though, so a standard frame, provided I can get one in a custom size, would be fine. I want just a simple, narrow black frame with glass. The glass is non-negotiable as I need to protect the artwork. (Some of it is ~40 years old and was displayed at some point without frames, so they're kind of faded already and I don't want to make it any worse.) The pieces are all already matted (also on non-standard sized mats) and I do not want to try to remove and re-mat them, nor would I want to cut the existing mats if at all possible.

Anyway, standard sized off-the-rack frames don't come in anything close to the right sizes. Custom framing places seem to charge an arm and a leg, and I don't want to be out ~1K to frame these things. (Also, I don't need anyone to actually frame/mat the artwork for me; I just want the frame and glass.) I have found a couple of places online that sell custom sized frames for reasonable prices but they don't come with glass.

So, has anyone done anything like this? What are my options? Is custom framing the only route? Is there somewhere that I can get pieces of glass cut to my specifications?

Some things that have been suggested to me already - has anyone tried these?
--look in thrift stores/discount stores for cheap framed art, which is often weird sizes, and just cannibalize them for the frames.
--do some kind of double mat situation that would allow me to fit them into larger, standard sized frames.