Now here's an interesting notion: custom mattresses. I came across a short blurb on California-based McRoskey Mattress Company a bit ago and was intrigued by their business model. They make custom mattresses for people who own old and/or antique bed frames, many of which were built to custom specifications and can not "receive" any of the current standard mattress sizes (twin, full, queen and king).
This interests me because I recently inherited a very old bed frame made by my great-great grandfather, who was a woodworker. I have yet to assemble the frame in my new place so I don't know yet if it will need a custom-made mattress. I'm hoping it doesn't, but it's nice to know that the option is out there.
Cost, however, is another matter. Mattresses themselves are not cheap. I can't imagine that a custom-made version adds any less than $300 onto that price tag. That's a guess, of course.
I'll keep everyone posted on whether or not I need to go this route. And if you do, now you know one of your options!