You need to get a curtain rod bracket. Home Depot has them for 47 cents each. Here is a link that might be useful: Single Curtain Rod Bracket

I agree with Annie. We have a similar situation and we placed the rod at the proper height for the lower ceiling and then just carried it around to the other wall at the same height. Your eye will stop at the rod and the ceiling height differences won't even be noticed.

Wood closet dowling. I think it might come in a 2"diameter, and up to 10'-12' in length. It's sold by the foot at Home Depot or Lowe's. I've used it several times for heavier draperies which were lined ans quite wide, and it worked like a charm. It's much cheaper than an extra large store bought rod. You will also need to buy brackets for the ends as well as one in the middle. I use wood ones which are sold in the drapery hardware department. You can also paint or stain your rods/brackets, moreso the brackets since they will show.

This one goes to 240", https://www.bedbathandbeyond.com/store/product/revel-adjustable-window-curtain-rod-set-in-black/3247792?poc=211183 For custom there is this on Etsy, https://www.etsy.com/ca/shop/AdyEscalante?ref=listing-shop2-all-items-count&section_id=11691672