I recently ordered a 0-1A and a 0-100ma analog panel meter from ebay.
I'm assuming both require external shunt resistors.
Commercial shunts I've seen are available for meters 5A and above.

Do these meters require external shunts?
Do I have to make my own or are there commercial shunts available for these meters?

 

If the scales on the meters say 1A and 100mA then they probably don't need external shunts.
If you have a meter with a diode check range, connect across the meters and if the pointer moves almost not at all then they have internal shunts.

 

1) use any proper shunt, the nail, steel wire, nichromium wire, cut-out platelet etc, but try to not wind it much to avoid inductive reaction. Only the tricky job is to calibrate it then.
2) avoid to screw shunt straight to the measure-head, if contact will loose, the head will damage. Instead screw the shunt in the main current path, and to head let go thin side-branch wires.