I love the lookout seats and I think the following websites will help you lmake your decision.
http://www.snoozer-dog-beds.com/sizes.htm http://www.snoozer-dog-beds.com/
I purchased mine on ebay (watch the shipping charges) but I know we have YT members who sell these in their stores and they offer YT discounts. You can also purchase direct from the above company.
Hope this helps.