I recently came across a really fine quality weatherproof SAE connector on a dealer's demo (used by them to keep the battery charged up): 18 ga wire, 20" long, complete with a good cap and a tight junction seal. The 'stock' connector for my electric vest is kinda mediocre, so I tracked down and bought one of these:
Optimate SAE-71 Weatherproof Connector
I got it from Polar Battery, 1259 Boundary Rd, Burnaby 604-294-1891. SG Power in Victoria are lised as the other lower mainland distributor. They had to order it in, which took about 2 weeks. Total cost, tax in, was $11.09.