Chrome screws...chrome metal polish with a kitchen scourer(one for non stick pans) so it doesn't remove the plating, polish off then wash in warm soapy water and dry in a warm oven.
The screws will be available from a fastener suppliers, I doubt very much that bass manufacturers would use there own bespoke screws as they would cost a lot to be engineered.
If you take one to fastner supplier they will use a thread guage to ascertain the type you need.
