I am 163cm tall and cannot wear the 85cm strap cross body. I ordered a 105 cm, wider canvas strap from Hermes for that purpose (also to wear the K32 more casually). Here’s some pictures to compare. Unfortunately they are not very clear but hopefully it shows that, with both straps, the bag hits the same spot on my waist/hip. The pic with shorts is with 85cm shoulder carry and in leather jacket 105cm cross body. HTH.
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ETA: To answer OP question,
I spend so much on the bag, I figure I might as well spend a bit more on original parts. I chose black also so that I can wear it with other bags (eg. the future dark blue Bolide 30). I think, unless you’re aiming to change the look dramatically with different or pattered straps each time -and therefore getting a few-, it’s worth getting one directly from Hermes. I ordered the strap and it took 6 months.