I'd try to email fishstreet.com since they sell these as well. If they don't have replacement heads and tubing, I'm sure they can get them from the manufacturer for you. I had a chinese dosing unit a while back and ordered it with replacement tubing and heads...a year later I needed more peristaltic tubing and they shipped some for a few bucks.
Also check ebay; if they sell that unit on there, chances are the seller also can send you replacement parts.