I noticed people asking where to get psyllium.
Some grocery stores may have it.
I stayed away from Metamucil, because even in the plain kind, they had sucrose.
Health food stores may have it. I found it in the bulk herb sections of stores.
If you can't find it locally, I'm sure there are places to buy it online. I'm just not aware of any things to consider in psyllium (places it comes from - Iran? India? - growing methods that matter, etc.)

Here's where I found it locally:
Trader Joe's (grocery)
Sprouts (grocery)
Sunflower Market (grocery)

Places I didn't check: Whole Foods, Wild Oats, GNC