I use the Cambro 12189CW135 4-3/4 gal Polycarbonate Food Storage Box @ $17.79 and the lid Cambro 1218CCW135 Half-Size Flat Lid for Food Box @ $6.79. I got them at the FoodServiceWarehouse.com site. I am sure there are other sources, however, this one was reasonably priced. I plan on cutting a hole for the Anova (well maybe I will) sometime. So far I have just been just covering the container as best I can with the lid and using a strip of tin foil to bridge the gap. What I like about this is that I can use the box and lid for other food storage needs. It has virtually eliminated the evaporation issues.
There are other great containers available from Cambro that are useful for smaller meals. I have not got anymore yet as I use a stock pot for most other things. Evaporation only seems to be an issue for the longer cooks and possibly for vegetables that require higher temperatures.