gotta love the sbmm SUBs, that price figure is definitely a steal! How are you loving the ax3? I'd suggest you don't put the tone zone in there because, those pickups are really mid-heavy and suits brighter-sounding guitars better, like alder-bodied guitars. Back to the SE HFS, well you've said the australian ebay doesn't have those pickups on sale, so you probably need to look at the international ebay page.
if all else fails, look for ESP LH-150 pickups, they're the same ones as the PRS SE pickups, also I'm not sure whether are they same as the "PRS-designed Treble and Bass" or "PRS-designed SE HFS and Vintage Bass". Just that the only beef you might have with it is the ESP decal on the pickup bobbins :dontknow:
One more thing to clarify on fitting it in the AX3, the AX3 uses a 5 way switch if i'm not mistaken and you could get single-coil tones from it in the 2nd, 3rd and 4th position. That means the stock pickups probably have 4 conductors. The PRS SE HFS from older 2010 or 2009 SE Custom 24 that has no push-pull coil split has only 2 conductors, which means you probably can't get it to coil split. Take note of this before buying or else you might have to go through hell to make it work or you could lose the singlecoil tones. Just aim for 4 conductors, not 2 conductors.