I have some Stainless Steel Reservoir Aerators I've offered on eBay.
They work very well and unlike stone aerators, they are pretty much unbreakable. It's the perfect alternative!
Item# 170596457712
You can check them out at this eBay url address.
Hydroponic or Aquarium Aerating Element, MOTT - eBay (item 170596457712 end time Feb-27-11 11:10:44 PST)
Take care!
Alan