I've been getting it from Chemistry Store, but the price has gone up there too. Still, it's quite a bit cheaper than the small quantities from the photochem places. But sodium citrate itself is still only ~$100 for 50lbs.
I'm curious, is this for kallitypes? I only use about 10-20g/l of citric acid in a 20% solution of sodium citrate, mainly as a ph tweak.