Front curtain

I decided to use snap buttons like on my old camper. Much simpler then trying to install a curtain rod where there was no place to install one. lol

A rod is going to be difficult as it needs to contour to the curves, be supported in enough places and still hold a curtain.

A slide is much easier as it's nothing but a flexible channel (plastic or bendable aluminum) that is supported externally or within the slide channel and can contour to just about any shape. The downside is you have to use matching curtain attachments that works for the type of curtain tape/slide you're using and the curtains can't be too heavy.

Contact Thor Industries. I am sure they will be able to help you.
If you want to talk to their customer service first , here are their contacts and best way to reach them quick. Good luck

There used to be a product called an "Easy Curtain" that was blackout nylon. It had 2 pockets that fit over the sun visors to support it over the windshield; then it wrapped around to the driver and passenger windows - those parts were held in place by closing a flap of fabric into the top of the window. The company is out of business, or at least they were when I was hoping to find one to fit a transit cab.

Re my Transit: I ended up using a jumbo sun shade in the windshield; and cutting Reflectix insulation to fit the side windows - I added some magnets to those (just taped them on) to hold them in place and they worked great. That would certainly work for the E-series, too

Hi Peter... try a fabric store or a drapery place.
john 'I am Canadian'