I am, i guess, fortunate that I can use many glutathione products. I try to alternate all supplements so that my body doesn't become too used to them.
For glutathione I alternate the following.
GSH + by Biotics Research
Glutathione Complex by Professional Preference
Lipoceutical Glutathione by http://www.gshnow.com.
I think I bought this from Brainchild Nutrition. They do mainly liquid supps.
I have also had IV glutathione but it seemed quite expensive and you had to drive somewhere to get it.