I use Eneloop or equivalent for the Disney monorails.
For N scale I mostly use eFlite lithium polymer cells from 70 mAH to 300 mAH. eFlite also makes a small USB charger. These are available from:
eFlite; Amazon; Tower Hobbies; Hobby King; and others
Tamiya, PN Racing and others make 130 size motors that fit in the Disney monorails.
Gizmoszone is the only source I know of for the small gearhead motors. My N scale monorails use the 6mm 25:1 type. Gizmoszone also sells gears, shafts, and other parts that we may use.
Didel makes small motors and gears and mostly sells through one of the listed suppliers below.
DelTang makes tiny 2.4 GHz radios that are designed for trains, these are what I am using now. Direct sales in the U.S. at Deltang.co.uk
Plantraco makes small 900 MHz radios that use short antennas. These are what I used from about 2009 to 2013.
BSDMicroRC is a supplier for indoor flight items and has plenty of parts that can be used in monorails.
BalsaProducts is another.
Didel makes small motors and gears and mostly sells through one of the above listed suppliers.
Walthers is probably the largest supplier of model railroad items
Tower Hobbies sells radio control items and model railroad items
Northwest Short Line makes gears and gearboxes that look like jewelry (to me anyway).
AvidRC has good selection and prices on ball bearings, Proto87 has flanged 1.5mm ID/4mm OD ball bearings.
Most of my small metric hardware is from Amazon (since they bought SmallParts) or NWSL.
Gears and wheels are from HO slot car suppliers, ScaleAuto and anyone who has BSRT products. Unfortunately ScaleAuto is not helpful to anyone not racing HO cars, I would go somewhere else, like Lucky Bob's or http://www.hoslotcarracing.com/
Updated Oct 2015