Besides Lamborghini Miura, there is one more marque that used the same indicator stalk...so if you can find someone parting a Maserati Ghibli or Sebring (late 60's GT cars), you'd be in luck--but the rest of us have to use the MGB stalk. (btw, not just us, its all Maseratinet has to offer, either).
Another that is close and actually sometimes available--As I can tell, Rolls Royce Silver Shadow used a very, very similar piece (including the same shape for the knob), but printed "Wash" (actuating the windshield wiper jets instead of the horn). https://www.ebay.com/itm/23380...7Ctkp%3ABFBMksOa4LVh
Luckily I've had mine, but this is one of my pet searches for years. Search Ebay.italy, there are 3 listings there (one somewhat distressed in Germany, one listed as NOS (and probably the last in the world, in Australia) but expensive, and another including the steering column that looks suspiciously instead like an MGB indicator stalk)...A year ago, on Ebay.it were 2 rebuilt ones, listed at ~800 euro...Lee