Edit,

I have made a test in my adminhtml.xml: this works completely, you should make sure to inherit all the structure top down, so not straight to products but from admin to catalog to products

<config>
     <menu>
        <catalog>
            <children>
                <products>
                    <children>
                        <lightbulbs translate="title" module="lightbulbs">
                            <sort_order>20</sort_order>
                            <title>Manage Light Bulbs</title>
                            <action>lightbulbs/adminhtml_lightbulbs/</action>
                        </lightbulbs>
                    </children>
                </products>
            </children>
        </catalog>
    </menu>
    <acl>
        <resources>
            <admin>
                <children>
                    <catalog>
                        <children>
                            <products>
                                <children>
                                    <lightbulbs translate="title" module="lightbulbs">
                                        <title>Manage Light Bulbs</title>
                                        <sort_order>20</sort_order>
                                    </lightbulbs>
                                </children>
                            </products>
                        </children>
                    </catalog>
                </children>
            </admin>
        </resources>
    </acl>
</config>

You should just add the menu from your own extension and make sure it has the same structure as in the adminhtml.xml from Mage/catalog. Copying corefiles to your local folder is not done in most cases. Alan storm has an article about creating admin extensions, you can use information from that article as a starting point.

http://alanstorm.com/magento_admin_controllers

You should just add the menu from your own extension and make sure it has the same structure as in the adminhtml.xml from Mage/catalog. Copying corefiles to your local folder is not done in most cases. Alan storm has an article about creating admin extensions, you can use information from that article as a starting point.

http://alanstorm.com/magento_admin_controllers

You can read the following in the article:

  <adminhtml>
    <menu>
        <tutorial_menu translate="title" module="adminhelloworld">
            <title>Tutorial Menu</title> 
            <sort_order>9999</sort_order>
            <children>
                <first_page module="adminhelloworld">
                    <title>Our First Page</title> 
                    <action>adminhelloworld/index/index</action>
                </first_page>
            </children>
        </tutorial_menu>
    </menu> 

Appoligies I did read it wrong, will check the rest the first difference I see is that your menu does not have an action at the moment.