Supply is no problem.
As you leave Vamos, towards Kalyves, the big shop on the left 200m or so past the petrol stations usually has a pretty good selection of sombas.
Failing that there's a shop on the Armenoi road as you leave Kalyves, on the left. Can't remember the name but it's the one before Maria Zilimbinaki's. They probably have lengths of flue pipe outside.
There's also the agricultural co-op next to the big IN.KA on the way out of Kalyves.
The biggest problem [not very big, really] with fitting is knocking the hole through the wall. If you don't fancy DIY you could find a jobbing builder or, probably the best bet would be to ask the suppliers for a recommendation. They're bound to know someone.
If you don't find anything you like locally, there's any number of shops in Xania.