Where can I buy live yeast? Who sells it? Can I buy it non-commercially? Does anyone sell it online?  I've found it difficult to find, at least in the United States's grocery stores. 
Both Red Star and Fleischmann's produce fresh cake yeast, but as it is a perishable item with a limites shelf life and a need for constant refrigeration, they limit their sales area and state so on their websites:     This traditional form of yeast is found in the refrigerated section of the grocery store. Due to its short shelf life, it is available in limited areas only.   (Fleischmann's)      Cake Yeast is available in limited markets in the midwest and northeastern U.S.   (Red Star)   If you happen to live in those states, remember that fresh yeast needs refrigeration, so it will not be in the baking isle with other dry yeast types, but in somewhere in the refrigerators. Ask the shop assistants.   Some users in other forums report that, according to their observation, some stores stock fresh yeast during typical baking seasons like Christmas, but not during the rest of the year. I can not comment on the correctness of that claim, but as I read it in various places, there might be a grain of truth in it. Even stores "in the fresh yeast area" are taking a small financial risk stocking it - it's perishable and the standard consumer buys the dry yeast they are familiar with.  If you are out of luck (geographically speaking) I suggest keeping your eyes open for small ethnic or artisan bakeries. Fresh yeast is available in larger units. If you find a bakery using it, asking very nicely might get you the desired ounce or so. Note the conversion rate - you will need about 3x the amount of dry yeast by (weight).  Buying fresh yeast online is probably a futile attempt - where the manufacturers refrain from shipping truckloads of the stuff, an online retailer would have to go through an unreasonable amount of trouble to ship 2oz yeast and keeping it cool while doing so.  