http://www.themaritimeguardians.com/coldfusion/lightships.cfm
Also Google the web site "Lightship Sailors" , there are a number of links from that web site, including USCG Headquarters that has photos under the CG history office.
Woodland Scenics is a company that produces "block" white lettering in dry transfers, they are easy to apply and if you mis align them just remove them with Scotch Tape. Also a good hobby shop has water slide lettering decals for both military and model rail road projects.
Don S. is spot on, you can always print your own on a home printer just follow his good advice.
Having served on a lightship here's a little tip: most folk are not aware that when commissioned, a lightship has weld beads applied to the hull sides that outline the letters to its first station (NANTUCKET for example). This aids in painting the white letters but as the lightship moves around in its career another station name is painted on its sides but the original weld beads are still visible close up with the new station name painted over it......