i bought a new foam base and had it fitted by a trimmer

i think the foam cost $190 and the trimmer about $100 i think its a fairly straightforward job, for a trimmer, you need the special pliers they use to fit the retaining rings.
(just checked the invoice they Cost $160 USD, and landed in Australia $225 each)

i got them from BMA importers & Distributors, i found them great to deal with and generally cheaper that the prices quoted on realOEM

mine are sports seats so a little more involved. although no heating

i had both passenger and drivers sides done and it turned out perfect, i would think you could get them rebuilt, but i believe you will get a better job using the originals