Possible yarn subs

I’m making this top : http://www.berroco.com/exclusives/granite/granite.html for my Mum’s christmas present, having a bit of trouble subbing the yarn - can’t get berrocco over here, unfortunately. It uses a railroad ribbon I’m pretty sure I can find an alternate for, and " round, knit ribbon with unique qualities of touch, elasticity and stability. A hosiery-like tube of silk and rayon encloses a core of airy nylon roving" . What should I look for - another ribbon type or a rounded strand?
Thanks for any help