You can find all sorts of metal and plastic 'stuff' at a Home Depot type store, but don't forget to snoop the local hobby shop. The folks who own them are generally experts at crafting and building little cars and airplanes. Real MacGyver types. They have tons of metal and plastic bar stock, plate, and tubing for things like petcock stand pipes. Tons of small springs and of course lots of itty-bitty screws.
The cosmetic counter at a dollar store will get you paper emery boards and metal points files. Nail polish remover is just acetone in small cheap bottles. My favorite is a bottle of clear nail 'topcoat'. Comes with a built-in brush and will seal anything. Use it to seal electrical connections, prevent the odd bolt head from rusting, seal up a leaky gasket or grommet.