I want to make a scale that can weigh multiple objects with about 0.1g accuracy. I can't find something suitable from digikey or mouser and it seems my google-fu isn't up to snuff. Where is the best place to find this?
I think the device you want is called a "load cell" or "strain gauge".
Complete device with load cell : digital lcd scale 500g portable for sale | eBay
Only the load cell: load cell -tester -cable for sale | eBay
See http://cerulean.dk/words/?page_id=42
The INA125P stably amplifies the output from the load cell, but you still need an AD converter if you want more than the 10 bits of precision the Arduino can provide.
All in all it's not an easy project.