1) The plugs into the QSI programmer programming track connection:
2-position Connector Plug Terminal Block, 3.5 mm.
Weidmuller #1615670000, Digi-Key 281-1054-ND, Price $2.21 ea.
Mouser doesn't carry it.
2) Wire-end connectors for the Q1/Q1a decoders boards:
2-position, JST ZHR-2, Digi-Key 455-1366-ND, $0.068 ea.
4-position, JST ZHR-4, Digi-Key 455-1202-ND, $0.09 ea.
6-position, JST ZHR-6, Digi-Key 455-1129-ND, $0.15 ea.
8-position, JST ZHR-8, Digi-Key 455-1199-ND, $0.19 ea.
3) Crimp-on contacts for the above:
JST SZH-003T-P0.5, Digi-Key # 455-1281-1-ND,
Price $0.34 for quantity 10.
4) Generic NMRA Decoder 9 Pin Connector
9-position JST ZHR-9, Digi-Key 455-1196-ND, $0.17 ea.