I can highly recommend Ortlieb bags.
There are plenty of models and sizes.
Family owned company with highes quality and service standards.
You can get any part in the aftersales...

https://www.ortlieb.com/de_en/waterproof

1973 2CV AK400 Ralley
1985 plus 4 four seater
1992 Peraves ecomobil
bicycles (pedersen to recumbent)