I'm not sure of the route you have planed but Mica dam ( creek) area is a dead end road that you get to from Revelstoke.
I have been drunk through Banff, Lake Louise and Kootenay Natinal parks for the last month helping my kids move back to BC and there hasn't been one available campsite with full hookups for weeks now. There could be sites available in the non service campgrounds, so you will have to check. You can not " boondock" in any national or Provincal campgound period.
Also the Provincal campgrounds in BC in the main tourest areas are also booked solid. Your bat bet is to travel on roads less traveled and then do as I have since I was a kid with my parents we stated driving at sun up and "tried" to park by 10 or 11:am at the latest.
I live in the Kootenays and we are pretty lucky that a lot of people don't like driving up and down over mountain passes and or drive on narrow roads with lots of curves. On the July 1st ( Canada day weekend) all campgrounds that we see around us were full. Now it has tapered off, but that could also have something to do with the weather as it has been wet.
Stay in the back roads, stay away from the populated areas and park early is your best bet.
Soup.