Digital BW, The Print

Hi,
I am new to this group, starting my digital b&w work...

As I succesfully unclogged the print head of an old Epson 3000 (which
had been out of use for 2 yrs) recently, and practised a little with
filling cartridges (quite easy actually ;-), I'd like to fill with 4
black/grey inks.

Which are the bulk inks that you folks could recommend, and where do
European printers purchase them.

I apologize if my questions are too basic and already answered
elsewhere; in that case I'd be grateful for redirecting me...

Thanks
fotojali