I have seen macrame books back on the shelves at Michael's. I don't remember seeing them since the '70s! I have looked for some new books over the years but gave up. I haven't been able to find any macrame rope either. I finally switched over to crocheting. I kind of miss my living room floor covered in rope!
I loved to macrame back in the day, too. I made a hanging table that took miles of rope, and about a million wall hangings and flower pot hangers.
I always did macrame using bailing twine since I had a lot of it. That was when the twine was made from sisal. Even when the twine went all different colors of poly some still used it for macrame. I know a lady that used those thin brown plastic grocery bags for macrame projects and made bags with shoulder straps using the macrame technique. Just about any hardware or craft store should have a natural twine that would work for macrame. I see several places online that have natural twines you can use for macrame. Variety stores sell a natural fiber twine that would work. It is usually over in the shipping supply dept. There are YouTube videos on color poly baling twine and macrame.