Question, are toilet facilities available to the crew? Seriously, I don't know.
Sadly, in the 60's Lockheed proposed a seperate cabin up front, with toilet, food and drink, and with a seperate exterior door such that it was physically impossible to get into the cockpit from the passenger section.
Airlines and FAA nixed the concept.
The crew uses the same lavs as the passengers. There is no provision to for crews to answer the call of nature on the flight deck. I guess we could always retrofit relief tubes into the cockpit (hey, it works for the military) but what would we do for female flight crew members?