For your convenience, you can purchase a durable version of the Mechanical Disk Brake Tool using this link: Shapeways Store
Shapeways offers direct printing services, and allows us to provide specialized products to our customers. These products are offered at-cost, without any markup in price. They are print on demand and the moment you make the purchase they will print and then ship the item so expect at least a 10 day delay (more information when making the order)
You may also use a 5 mm Allen wrench.
Link: Maintenance - Brake pads