Can't speak to making a vertigris patina on copper but I have made
vertigris for adding to glue on Tudor period arrows.
I just let some small pieces of copper pipe (household plumbing
pipe) sit in plain white vinegar until the solution stopped smelling
of vinegar and had turned a dark blue-green colour. If you were to
put some vinegar into a pump-spray bottle and spray it on the piece
and repeat until you had the effect you wanted.
I have also heard of "aging" copper roofs with a similar setup but
with dilute hydrochloric (HCl) acid instead of the vinegar.
You should be able to get the HCl from paint supply (preparing
concrete for painting) or plumbing stores (may be called Muriatic
The HCl isn't dangerous as long as you treat it with care and
remember add acid to water when diluting. Do it in a well ventilated
area as chlorine gas is a possible byproduct of the reaction.
PS it is thought that the vertigris was used as a fungicide/pesticide
to protect the hide glue from being eaten by microbes/other pests
while in storage or during transport.