Hi!
I make my own aluminium shims!
It's easy!
Just use a divider with a knife blade (there are small blades made especially for dividers).
I use 0.1mm pizza foil.
Put some masking tape where you intend to put the sharp divider point and slowly spin the divider round until you have a small indentation in the foil! But do not ! Do not! try to cut through the foil yet!!!!!!

Now ,when you have two ring formed indentatiions in the foil looking like a shim ...you just take the foil between your fingers and began wiggling it!....
After a while the shim will get loose from the rest of the foil! if not! Just keep wiggling untill it gets loose!!!!
It takes some practise to make the correct inner and outher shim diameter.But practice makes perfect!