BTW, I'm assuming that the OSD control is the same for the 1280EI. Do you have the datasheet for the 1024E so I can compare?
I took a quick look for the connector, but didn't find one by the manufacturer listed in the datasheet (Yeonho), but I'm sure I can find one that fits. It would be cheaper and easier if you don't mind cutting the cable and soldering it directly to the board.
Buttons like the ones I have on my Dicon OSD board are cheap and easy to get. But you could pick any button you like.
Bill of materials is:
1 small board
1 two color LED
a few little jumper wires
That's like $10 in materials.
Now I could do it for you if you want. I'll be ordering some stuff to finish my project soon. I could add in your parts, then put this together for you. If you are in no hurry (won't be bugging me for it until at least 6 weeks has past), I'd just do it in my spare time for nothing.
If you want me to do this right away, it would cost you.