I purchased my empty 80 ml carts from Inkjetfly, these are great quality and fantastic value.
Ink manufactured by Image Specialists (USA) is top quality and hard to beat.
chubs380 (PrecisionColors) on ebay is the cheapest supplier based in Canada.
Octoinkjet is a UK supplier
The 3880 ink may not be listed so just choose ink for the 2880 (A3) printer
edit: check out Octoinks filler caps, these make life a lot easier, no messy syringes.