So I bought the worlds greatest tent a few years back and I love it! Its a Black Diamond Guiding Light that was discontinued back in 2010. Its a 4 man 4 season single walled tent. I only wish I'd a gotten a vestibule or two at the time.

I found this link last week and it gave me a ray of hope. Maybe the light house is compatible.
http://bushwalk.com/forum/viewtopic.php?f=13&t=7080

Then I asked Kim @ BD (who is awesome BTW) about her opinion.

This was her reply over two emails.
"Kevin-

Based on the link you sent me, the link you sent me was an old (already sold) ad for the Guiding Light and the Guiding Light Vestibule. The vestibule shown in the ad there will work great with your Guiding Light but we don't have any more of them.

I understand that it looks like the Lighthouse vestibule will fit the Guiding Light but it won't. You may be able to make it fit but here are the main differences. Where the Lighthouse Vestibule attaches is 7 longer than the Guiding Light Vestibule attachment location. So you will have more fabric than you need making for a loose fitting vestibule. The connection points will be the same type of connectors but they wont be the exact right location to have a matched fit with the tent."

LATER KIM REPLIED AGAIN WITH..

"I wanted to get you an update on what I found out about trying to use the Lighthouse vestibule with the Guiding Light Tent. It will NOT work. I'm sorry but its just not an option. I had two individuals who have tried to modify several different types of Black Diamond vestibules to fit the Guiding Light confirm that it is not possible. I'm sorry to be the bearer of bad news. Let me know if there's any other options or things you would be interested in pursuing more information about.

Kim Hall | Black Diamond Equipment"

This has been the best customer service I've ever gotten. We exchanged emails most of the morning.
Here is a similar discussion I started elsewhere.
http://www.mountainproject.com/v/wanted-bd-tent-vestibule-for-the-guiding-light/108098253

Any ideas? Anyone?