Where can i source a battery door for the dimage z3?

Check on ebay to see if someone is parting out a broken camera. Otherwise you will have to get it from the manufacturer who will soak you for it.

Have you checked the batteries ?

Choose the color here.

This is Konika Minolta DiMAGE Z3 complite Instruction Manual

Contact Sony they purchased Minolta a few years ago and have the remaining parts for the Dimage series cameras

please use my real email account to deal with buying my battery door. $10 or for $25 I'll install it for you. keithtracypierceATcomcast.net

I am no expert at all, and the only camera I took apart was a Z3, which I did only to remove the battery door. dunno if Z3's similar to Z1; it IS similar to Z6 though.
Just a guess: electrical contacts at the viewfinder switch?

I opened a Z3 to fix a loose connector. I posted some pictures here:

http://forums.steves-digicams.com/forums/view_topic.php?id=573231&forum_id=20

The DiMAGE Z3 employs three types of metering mode: multi-segment (256-segments), spot metering and center-weighted.

In addition to AA size batteries (alkaline batteries, Ni-MH batteries), a dedicated AC adapter (sold separately) can be used. The other AA size batteries cannot be used.

Approximately 335g, excluding battery and storage media.