Thought I would post this since it might help someone else. I recently had to buy belts for two Thunderbolts, and here are the part numbers and prices*.
A2 series blower, (5M), three belt: part #: B48 $12.00 each
A2 series blower (4M), three belt: part #: B54 $13.95 each (price approximate, industrial only belt)
C series blower, two belt: part #: 3VX560 $15.72 each (price approximate, industrial only belt)
Rotator drive belt (all models) part #: 4L320 $5.95 each (industrial/ power equipment belt)
I recommend buying belts from NAPA or a reputable industrial belt supplier. Most auto part stores don't carry the industrial only belts and will give you the wrong one every time.
*These prices are from April of 2010, so current prices may vary.
Many of these parts are available at Mcmaster Carr. http://www.mcmaster.com/#
Here are some more parts I know off the top of my head. We'll be adding stuff as time goes on:
4M blower QD bushing (slides on shaft, pulley attaches to bushing) : Type SD, 7/8 shaft
5M blower QD bushing: Type SD 15/16 bore, bore has to be reamed out to fit since the blower shaft is a really odd size.
Tbolt flange is just a regular flange for a 3 inch pipe. They are available in both forged and cast versions. I prefer forged since it's tougher and not as brittle as cast.
Blower frame U bolt is for a 3 inch pipe and has 1/2-13 threads.
Tbolt chopper motor/model 2 taper pins: #5 X 1, available in stainless from Grainger.
Recommended grease for the blower is Shell Gadus V220. I buy it by the case and use it for the chopper tube also since it's cheap and works well.
Lifting eyebolts for the XT22, STH, SD-10, and various other Federal sirens are shouldered eyebolts 1/2-13 and about 1"-1 1/2" long. They are available in stainless steel also.
AR/AF timer parts:
Microswitches: Mcmaster Carr part #779K62 http://www.mcmaster.com/#7779k62/=vyp52s
Relays: Mcmaster Carr part #7170K14 http://www.mcmaster.com/#7170k14/=vyp5sq