Take a look at the eMac pull apart where they remove the motherboard and hook up a VGA monitor to the motherboard.
So I guess pull apart the machine, find that connector. Wire up extensions to both and bring out to a VGA switchbox. Then you can use other ports on the switchbox to as a VGA input.
You do know you can get 17" VGA monitors for like $5 at thrift shops around here?
The internal monitor connects to the pav using an ADC connector. ADC to VGA convertors are redily available for around £2. Only thing is, i think the machine has to be running for the monitor to have power.
Alternatively you could swap your emac with me for a monitor