I believe if you edit the metadata (you might need to add XML metadata) you can either specify one of the columns as a primary key (which will result in selectors, i think), or you can set alwaysShowRecordSelectors=true. I think any of the three things below would do it (see comments inline):

<tables xmlns="http://labkey.org/data/xml">
    <table tableName="" tableDbType="TABLE">
       <!--I think this alone will do it-->
        <pkColumnName>MyColumn</pkColumnName>
        <columns>
            <!--Another way to do the same thing as above-->
            <column columnName="MyColumn">
                <isKeyField>true</isKeyField>
            </column>
        </columns>
       <!--and I think this will force it even w/o a primary key-->
        <buttonBarOptions alwaysShowRecordSelectors="true">
        </buttonBarOptions>
    </table>
</tables>