Active Users

I am new to GA. I have one GA account. I have created twenty properties in this account. Each property represents one of twenty unique e-commerce websites I own. All twenty e-commerce websites reside on one server. The server has one url address, and each e-commerce website on that server has that same url address, but is tagged with a unique id# at the end of that url. This unique id# is added to the url address in order to separate the e-commerce websites from each other. When I select one of the 20 properties I have created it shows me data from just that individual e-commerce website... as it should, and as I need. Here is my problem.. When I first opened my GA account I created one property. That one property treated all 20 individual websites as one big e-commerce website. When I had only this one property, when I was in "REAL-TIME" view I could see the combined total number of active users from all of my twenty unique e-commerce websites. I need be able to see this number. Every time I created a new property, the active users from that property no longer show up in the combined active users total property. Is there a way to keep the twenty properties I have created, but create something in GA that I can see in a "REAL-TIME" view the combined total active users from all twenty websites? Thanks for the help.

Steve