Mike, you're nuts to hook the top off straight to the RO/DI system. If there is ever a failure all of a sudden your fish are swimming in freshwater! I know two people that have crashed their tanks this way. Imo, not a good idea.
Hustler, I use a 5 gallon pail for my 90 and it is a bit small for in the summer when evaporation is at its peak. I think you're looking for something close to 30-40 gallons or so if you have room. Running the line through a wall into an adjacent room is pretty simple. You could install it to run behind the baseboards if you want. Make sure the end of the top off line (the end at the tank/sump) is higher than the water level of the vessel you are pumping from otherwise it will gravity feed out of the vessel.
Dog food storage containers tend to be a good shape. Personally, I don't like use trash cans because they are often not food grade plastic. 65 gallon drums work well too (I use these for mixing saltwater).