First, I think we should be absolutely sure which brakes you are talking about. There are 2-pot and 4-pot AP Racing brakes for the MGF/TF:
The 4-pots are quite common but the 2-pots much less so. People sometimes mix them up. I don't know whether they use the same pads but it seems unlikely.
If it is the 2-pot calipers you have I would try contacting Darren Hardy at mgfntfbitz.co.uk as I am pretty sure he has the parts for AP Racing calipers at competitive prices.