Just buy the Gerber Tool Kit adapter--it fits on my ST300, as I had an MP450 (apparently Walmart exclusive version of the MP400, which has a file in place of scissors). The original Tool Adapters, which were made to fit into the pliers, instead of over the Phillips aren't designed for modern Leathermans such as the ST300. The newest it fits, apparently are the Zytel models introduced in '04, such as the Kick.
I personally just carry a small Chapman offset screwdriver kit to cover jobs in which my multitool doesn't have the right bit, or it requires too much torque (busting an $2 bit is far better than a pricey $25 or more multitool).