I have purchased 3 Volos on ebay and they all came with a rain cover.
I would assume you could buy the cover separately.
*It didn't rain at all our first trip and I wound up leaving the covers in the room after our first two days. I thought they were fairly useless, however... We were there during the two weeks of non-stop rain last May. Those stroller covers were absolutely THE most valuable thing we owned. They never came off the strollers the entire trip.*