I found a great solution, I think on IRV2. Get a piece of 1/2" sched 40 PVC. Cut it to a length that's a little shorter than the rod section of your strut when open. Cut a lengthwise slot wide enough so that you can snap it onto the rod but small enough that it won't fall off.
When you close the door, push it with your finger so that it will slide it over the barrel portion of the strut as the door opens.
When you open the door, it will drop down onto the rod portion in a "cocked" position and hold the door open.
It's much cheaper than a replacement strut and will never wear out. The struts on my 2002 Itasca Suncruiser 35U are all starting to fail and I'm doing this for all of them except maybe the one or two that I'm in and out of all the time.