I have been complaining about the same thing from the get go with my dealer. Some models come with the arm and some don't. Pretty frustrating to me. I am still waiting on a response but I will be putting one on my rig before too many more weeks. The local dealer has one that they use with another type of camper that has a locking mechanism built in. If I can find out what kind of mount it is I will try to post back up with the name.
My dealer tried once already to put spacers behind my wood mount to turn it down some. After that I could see it when sitting on the couch and in the table chairs without the dark spots at the top but I still can't lay on the couch or the air mattress and watch movies because it is too dark to see. The best place to watch the TV when I bought the camper was laying on the bunk over the garage. You couldn't even see it from the couch at first because it was angled flat and more on the upward angle rather than directly flat.
I have looked at this mount on ebay.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=380015110435&ssPageName=STRK:MEWA:IT&ih=025
I checked the specs for my TV here
http://www.olevia.com/en-us/Products/OtherModels/LT26HVXLCDTV.aspx
The mount can support up to 80lbs and the TV weighs 44lbs gross and 31lbs net so I am guessing that the gross is including the base plate that is indicated in the picture on the site.
This mount seems to be stronger than some out there. I have been trying to decide what I would use for straps but haven't completely decided yet. I used boat pad eyes in the openings above my cabinets and used bungee cords to keep stuff from coming out of those areas. I will probably do something similar to the TV just to keep it from swinging out too far during transit.