Classic Elite Montera
is an aran weight yarn, 50% llama/50% wool. Stitch gauge is 4st per inch.
When you look through your stash, or go looking in an LYS, or go looking at Joann's or Walmart...look to match the weight of the yarn. That is to say...the thickness of the yarn. Aran weight, or any yarn that the label says the gauge is 4st = 1", or it might say 16st = 4".
I would avoid novelty yarns, fancy textured yarns.
Just a nice smooth aran weight yarn. Cuz that's what Montera is.
I'd name names...but it's impossible for me to know your budget, and your access to local shops.