Matt, are you saying that you want someone to make the OEM clock display MPG? Or do you want someone to mount a MPG display into the OEM clock location?
I do have a spare OEM trip computer from an 88 legend that I would be willing to let go for cheap if you want an OEM Honda MPG computer.
My question... can SOMEONE make something simple that will turn this into a MPG display?
If it's a typical highly-integrated-for-cost-savings clock, no. At best you might be able to reuse the bezel/mounting stuff/display; everything else would be a ground-up build. Ergo, not "simple."
But putting an MPG display in that space (whether reusing parts of the clock or not) is certainly do-able.