Basically I want something that looks like this after a week or two - http://files.getdropbox.com/u/455762/ex_irish_moss.jpg

But at the same time is cheap to buy in bulk.

I'm not certain what you will be doing with this seed, or why you've posted your question in the Ornamental Grass Forum, but there are lots of OG seeds which are tiny, and can be bought cheaply in bulk.

An example would be Schizachyrium scoparium (Little Bluestem). There are ~260,000 seeds to a pound, and with careful shopping online, you can buy a pound for under $14 + shipping.

Try using Google, and searching for "native grass seed."

I haven't explained my situation well... let me start over. Basically I'm working on this art project where we need to arrange seeds into different patterns and then film the seeds sprouting / creating a pattern / drawing. This will really work with a lot of different kinds of seeds but the tricky part is I need to keep the detail really fine even when the whole layout is going to be massive. Hence after trying a bunch of seeds I've found Irish Moss to work nicely, it has tiny little seeds that produce tiny little sprouts (hence great pattern detail). Only problem is buying Irish Moss seeds gets pricey really quickly... So basically I want cheap tiny seeds that will grow like this - http://files.getdropbox.com/u/455762/ex_irish_moss.jpg

Any help would be AWESOME!