I agree with 2birds1stone. It's simply not critical enough that you really need to worry about it. You'll have exposure to real estate (indirectly) through your standard equity portfolio: things like homebuilders, home furnishing stores, carpet and wallpaper manufacturers, etc.
I wouldn't sweat it. My wife and I have basically all of our networth in long-term investments - with no REITs in our asset allocation - and we're renters just like you. If you really, really decided you wanted / needed REITs, the typical suggestion is something like 5-10% of your portfolio.