I've just found this: (no wonder i am having trouble buying a proper tool). Looks like its going to be a real project to source... because of the security thing.
"Tri-Wing®
Tri-Wing® is a winged security profile consisting of three edges. Thanks to its unusual, three-wing design, it is intended exclusively for use by professionals.
This profile is primarily used in household appliances and in the aerospace industry.
Licenser is the Phillips Screw Company"