[broadgage]

You may be able to find them from a vehicle spares supplier. Widely used on older cars for dashboard indicators, and sometimes for front marker lights that are built into the headlight housing.

Remember though that vehicle lamp holders are almost always earth return and therefore unsuitable for dangerous voltages.

EDIT to add, loads of earth return types for sale on ebay, and also a couple of insulated types with two terminals. Suggested search "ba9s bulb holder"