I'm in the UK so these are the local suppliers I used for the parts.
General resistors, caps etc from Radio Spares: http://rswww.com/
1 Gig resistors are expensive, especially if you buy the wrong ones (like I did).
On the left is a "cheap" one: about £1.50 each. RS stock number 247-7856. These fit in the space on the PCB.
On the right is a big blue one that is tricky to it in the space on
the PCB. these are about £4.50 each.
Lundahl transformers and Mogami tube mic cable came from Canford Audio
http://www.canford.co.uk/
PCB sockets came from Farnell:
http://uk.farnell.com/
For capsules, I'm using "spare" CK12 capsules from AKG414 mics - these came from Arbiter group, the UK AKG distributer
Valves / Tubes - At the moment the G7s have got Philips / Miniwatt
EF86s in.
I buy most of my tubes from either watford valves or colomor;
http://www.watfordvalves.com/
http://www.colomor.demon.co.uk/