Battery holders that we use in some of our kits. What we like about these are the leads that come pre-attached, ready to be soldered to a PCB, or attached with your choice of connector.
Two mounting holes to accept flush head screws. You can also use high adhesive double-sided tape, or a glue gun to attach to your project or prototype.

Simple 2 Cell AA Battery holder square
This battery holder have two wires 6 inch of 24-gauge leads that have 5 mm of insulation stripped off of the ends