i received some really great online service from ebay store http://stores.ebay.com.au/essentials-petsupplies2015
they are located in Qld, but they were happy to sell me just the heads off their sunsun filters to keep my shipping costs down. i didn't expect them to shave any price off the entire filter, but they did so without any asking and sold me two HW-304B tops (with UV bulb and glass) for $60 each and $30 shipping to Vic on the entire package. they are heavy, so i believe that to be fair.
they don't sell a lot, but do check them out before your next purchase