Personally, I prefer the correct vintage buckle. They're a pain in the ass though because they're 15mm instead of the modern 16mm, so it makes it harder to find a strap that will fit. I do believe there is an australian Ebay seller that sells modern aftermarket copies/homages (let's not get into that debate) GS buckles that are 16mm.
It's this one, though he doesn't seem to have any in store right now:
https://www.ebay.nl/itm/304724218755
But I would have no real problem using the buckle from a modern GS. A nicer alternative to the one you listed (in my opinion) would be something like this:
Another thing to make it more complicated: different vintage GS models had different buckles. The one you pictured is correct for later models, but not the 57GS and 62GS for example.