As far as finding "original" fergetit....
For the pop-up boot (as it is sometimes called) try a local awning
shop. If you still have even the scraps of the original they can make a new one for you.
For the lift tracks, look at heavy duty drawer slides at bigger hardware shops. Several on here have made new ones from that source.
And what is the problem with the window?
BTW: Here's one for sale
great camper trails west campster 15ft all original
They cost a bit more out here