I don't know the sizes but Members have said Ace Hardware has Copper Washers.

I use the Harbor Freight Copper Washer assortment and have been know to take a File to the inside of the Washer to get it to fit when they were too tight.

For the ALDA Fuel Injection shops will have the small Washers or maybe the Manifold Banjo Bolt size. They get Gasket Kits and do not use all of the Washers because the kits are made to fit a bunch of Models of IPs.
Where I used to worked we had about a 1 gallon Box of new extra Copper Washers and a larger one with extra O-rings not used in the rebuilds.

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84 300D, 82 Volvo 244Gl Diesel