1.) Yes, yes, yes. I do own one, a black one, and - as gloomy as it sounds - I got nice comments wearing it to a funeral (the event was quite laid black per the families wishes, but I ensured I was dressed appropriately) and it really is a great item to have. I would love a burgundy one too. They add texture to an outfit, and elevate the tie to a more acceptably casual level whilst still looking smart. Worn correctly, I do think a knitted tie can look as smart and appropriate as a silk one in more formal environments.
2.) as for where to get one, have you tried eBay? (I know you're an eBay whore like me ). I think others can help you in this department though as I don't really shop for ties. I have this tight woolen one from All Saints, however, if it counts as knitted (it's awesome)