Member's tip from Steve M: Use spring steel wire for flagpoles. Most vessels have an upright flagpole at the bow, and a sloping flagpole hanging out over the stern. These are two locations highly susceptible to damage, especially during transport. Use spring steel for the flagpoles so that if they are snagged they will bend without breaking. To make them safer for transport, make them removable. Fasten a piece of brass tube in the hull, and slide the flagpole in when needed.
Small metric screws.
If you need small metric screws and nuts among other things, Prime Miniatures in the UK is one source. They stock screws as small as 0.6mm diameter.
Confederation Marine Modellers
The kit manufacturers and the commercial market in ship model fittings can supply decent quality metal eyebolts these days. However; almost all are fairly large with straight, smooth shanks. Sometimes, whatever scale you are working in, there is a need for a tiny eyebolt that can take a good deal of strain. See this idea from the Nautical Research Guild.