I found a place sells all size sprockets.

GoldenMotor.com

Wevil Kenevil

Well-Known Member
Mar 4, 2022
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Sack a tomatoes California
AliExpress is selling sprockets that can handle 415 420 chain and start at 10 tooth and work its way up sequentially to 68 I believe is the highest one... Just in case anybody was wanting to go so fast that their poor little legs couldn't keep up with the bike... lol... 11 tooth cog in front and a 10 tooth in the back... weee!

I know that's way too small to even get the bike to move I was just saying...