Cant you tumble the old ones?

There really arent screw kits made for exact games.

However, if you look in your manual, youll find the sizes you need, and companies like Pinball Life, Marcos, and others will
have them to order alacarte. Order Extra.....If you dont have magnetic drivers, they are a big help.
I saw some on PBL on sale, or I use cheapy Harbor Freight, and glue a small round rare magnet inside...

If there is only a light oxidation, light tumbling/polishing wont remove the plating. If they are rusted, they are gone,

If you have a good local hardware store, almost everything can be bought there as far as nuts, screws, bolts, t nuts go.

This is your best bet. If you order screws from pinball supply places they will cost you a fortune.

My Fish Tales screws were all tarnished also. I grabbed them by the base and buffed the heads on a rag with metal polish, and the ones that were incorrect, missing, or too rusty I found at the local Ace Hardware.

I make a list of the sizes needed and order them on Ebay, I replace alot with stainless so they look nice.
I also have tried Home Depot but their selection was just ok and i had some quality issues

I go to bolt Depot and order the most common nuts and bolts by the 100. Way cheaper then hardware stores. Then tumble the rest and if anything isnt satisfactory I'll order from specialty shops.

I use Bolt Max for "S.E.M.S." style screws (these have the lockwasher built in) for dirt cheap by the bag of 100.

https://www.boltmax.com/products.php?cat=523

For other common screws and nylock nuts, I go to my local branch office of Tacoma Screw Products.

http://www.tacomascrew.com/Products/Nylon-Insert-Lock-Nuts/094-101_5

That's why I said good, not hd or lowes