Look up your printer model number on Alibaba. Or better yet, on Taobao (but if you don't speak Chinese it's a bit complicated). Your options depending on the printer you have are going to be :
Print heads conversion kits (a replacement of the complete print heads module with tubes feed from ink bottles attached outside your printer)
Refillable ink cartridges
Counterfeited Compatible ink cartridges that cost a fraction of the official ones while having 10 times more ink in them.
Now depending on where you live and the local laws it may or may not be legal to import those. In the country I live in there is no law against it. In most South East Asia the law doesn't care about that and if it does, law enforcement doesn't. :)