Oops my bad, you can't actually buy them in marts as far as I know, haven't played it for a while. You can buy some from this herbal shop in some town but it affects your pokemon's friendship. Forgot where it is.
The name's not ether, look in the description for the items, there should be one that restores your PP.
Just dowse for ethers or something, or go on gamefaqs and look for some walkthroughs to get heaps of ethers. Sorry can't help, my friend has my Pokemon Diamond.
Elixir Recovers 10 PP for all *Dowsing (PIIPII EIDAA) moves. *Iron Island *Lost Cave *Rt. 212 *Team Galaxy HQ. *Pickup (61-80). Ether Revovers 10 PP for one *Dowsing (PIIPII EIDO) move. *Pickup (31-50) *Eterna Forest *Rt. 215 *Mt. Coronet(south) *Rt. 220. Max Elixir Recovers all PP of all *Dowsing (PIIPII MAKKUSU) moves. *Valley Windworks (Dowsing, right side of the windmill behind the fence - you will need surf) *Mt. Coronet (North) *Pickup (91-100). Max Ether Recovers all PP of one *Dowsing. (PIIPII RIKABAA) move. *Victory Road (Second floor, north).
hahahahahahahahahah am I the only one that noticed that "stuff" is spelled wrong. PS I dont think you can by them... sorry.