Below you will find a link which will allow you to search the greater Houston area for any Realtor hosted and advertised open house that a Realtor has posted on the Houston Association of Realtors website.
As a Realtor and your guide :-), I would strongly urge you to either take a handful of your agent's business cards giving one to the hosting agent upon entering an open house, or immediately upon entry to the open house, tell the hosting agent that you are already represented by an agent (assuming you are). This protects your rights for representation, and it will also discourage an ethical agent from trying to pursue you to be a client of theirs. In addition, this will demonstrate your loyalty to your own agent, as your agent shows their loyalty and commitment to you.