Well done for sorting it. The later model bikes come with the rubber plug that John O mentioned. The calipers are the same design, so it is a legitimate replacement.
I modified a front pad pin from my 2009 model - the ones with the Hex head. They fit, but need to be modified slightly, otherwise they tighten against the shoulder, rather than the taper at the end of the thread.
They also need a short socket with no internal tapering - as the head is quite recessed. So a normal socket with the open end ground down. The same pin has been in use since about 2009 and has been completely trouble free.
Unlike the correct pins which gave me a lot of grief.