Don.....So far adding DEF hasn't been a big issue, but I like to be prepared. Surprisingly, I have yet to see a DEF pump in Southern California. During our west coast trips (only have had a DEF coach for six months) I've only seen DEF at one pump.
Just to be prepared, I bought a 2.5 gallon container that is designed for DEF and comes with a long spout. I leave the empty container in my bay and will use it if I find DEF at the pumps and need it. I bought the container from
this company. They have great info on their site and they're working on a small container with a metal collar. (Some pumps won't distribute DEF unless they sense a metal collar).
Lastly, I buy my DEF from the local auto parts store or Walmart. Just be careful with Walmart, so far, out of about 10 boxes, I have come across one that was opened and the seal was missing. It's easy for a low life to use the DEF, fill it with water and return for a refund!