So you have connected both the power button and the reset button leads to the mobo pins for the power button, and neither of them worked? And yet, a short with a screwdriver across those two pins worked OK? Seems very strange that BOTH buttons have failed.
Proximon had the best suggestion right off the top - just buy another momentary-contact pushbutton switch, drill a hole if necessary to mount it in the case front, and mount it. Detach the wires that serve your current front on/off switch from that switch (they are the right size and length and have connectors on the end already) and solder them onto the switch terminals. There is no real need to worry about switch polarity, and the current involved is almost nothing so there is no special grade of switch required. It just needs to close only when pushed, then spring open again.
If you're going to disassemble the front of the case enough to do this, take a very close look at what is going on with both old switches. Any chance it's a simple matter like a pulled-off wire?