Access to water and sanitation is a human right. It is not only fundamental for human dignity and privacy, but is one of the principal mechanisms for protecting the quality of water resources.
Canadian Occupational Health and Safety regulations state that "Each personal service room shall be cleaned at least once every day that it is used."
(Personal service room means a change room, toilet room, shower room, field accommodation or a combination thereof).
Anybody with arms could clean the office washroom, I feel like your employer is just making excuses because no one with a desk job wants to clean it.
Furthermore, you may receive a $300 fine. "No person shall urinate or defecate on a highway or in a public place except in a facility so designated for such a purpose." (City of Revelstoke Nuisance Bylaw 2083 2.3)
As you can see, I became quite invested in your bathroom dilemma. I fell down many Google rabbit holes. Please keep us updated. I wish you luck.