Note: I am based in England, so my suppliers have a UK bias.

End-grain balsa: Allscot Distributors
Carbon fibre products, epoxy adhesives and cutting tools: Easy Composites
Stainless steel nuts, bolts and washers: Westfield Fasteners Limited
PSU and Speed controller cases, toroidal transformers: RS Components
Other electrical components: Maplin Electronics
Laser-cut acrylic top plate, cut and etched PSU/controller front panels:  Cut Laser Cut
CNC routed MDF: CNC Routing
Replacement PT bearings, DC motor/controller upgrades: The Funk Firm turntables and accessories
PT Bearing repairs, adjustable feet, record clamps: True Point (UK) Ltd - Precision engineers