I would do what the post above says.
We have a 37 footer and the patio sliding door is the same as one from Lowes or Home Depot, ( but they come in various widths)
I have installed 5 sliding glass doors and it is a fairly easy job if you are handy.
Shims, mouldings and some good caulking are your friends!
I would get the cheapest I could find
Jack L
Jack & Nanci