Hi Chris,
I've been working on several 1/48th scale ships and here are some of the outfits I've found to be useful.
For fittings and weapons, check out QuarterMaster Scale Ship Fittings. Here's the contact info:
Robert E. Thomas
212 Greenbank Road
Fredericksburg, Virginia 22406
540-752-1623
qmaster4@juno.com
I am planning to order a bunch of stuff from him but haven't ordered anything yet. His stuff looks outstanding in the the photos I've seen.
John Haynes seems to concentrate on 1/96th and smaller scale fittings, but he also makes a limited number of 1/48th items that appear to be very good quality.
Also, there are a couple of online retail places I frequent; the Floating Drydock and Loyalhanna Dockyard. Both places retail various 1/48th fittings from several vendors. I have ordered many times from Floating Drydock.
Good luck with your endeavors in 1/48th scale ship modeling and keep us posted!

John