pugs

try gently heating the calliper .put it in a vice and try working the piston backwards and forwards,with a pair of slip joint plyers,or try a local garage and see if they have a high pressure airline and try blowing the piston out,but only use the last idea as a last resort,also i,ve soaked one in wd 40 for a few days as well .just got to keep trying it.hope this helps as mine did this a few times,i split the calliper and that works as well

try stealth brake discs there on the web or just bandits if there still going

best to find a mechanic who welds,or have a look and see if there any clamps on it and if they are loose,