RE: SH.18 parts
I believe the Landslide has the SH18 side exhaust slide carb. Here is a link to the exploded view of your engine.
[link=http://www.shengines.com/PTF/PT18S01BS.pdf]SH18 side exhaust slide carb[/link]
The part you need is the Head Button part number TE1803A. At HobbyPeople, I see the TE1803 listed, but not the TE1803A. The TE1803 is for rear exhaust, not side. It is possible they may be interchangeable, but I would not bet on it. I would check with HobbyPeople who luckily are on your side of the continent! By the way, if you find the TE1803A listed for an XTM engine, they are the same, so it would work.
You could also try John aka rclynx here on RCU. He sells XTM, although I do not know if he has that specific part. You can contact him through RCU or try his web site which has a phone number [link=http://xtm-dealer.com/]http://xtm-dealer.com/[/link].