Yes, any container will work fine. I used a 10 gallon container made for potable water for an RV or horse trailer. I spray painted it black, and it sits behind my tower speaker so it blends in with the furniture. BRS has a great example of hiding a top off reservoir in a foot stool or ottoman.
I really like the systems from autotopoff.com. They work well and are priced great. You would definitely want a 2 switch system. You want redundancy or you could end up flooding the house.
I use an aqualifter pump that is controlled by the autotopoff.com system to move water from the reservoir to the sump.
I then use a hose that goes from my RODI
Tanks in the laundry room to fill my reservoir, and for water changes.