I’ve found that the locksmiths in the higher income neighborhoods typically have the software/programmers if you REALLY want to avoid the dealer and find a genuine key online (as stated above, the cheap Chinese clones usually won’t mate.)
My GF is the absolute worst at losing keys…lost keys to the Mercedes a few times…once in SoCal, once in NYC, once in Atlanta, once here in Greenville…probably not coincidence that when calling around a locksmiths in Laguna Beach (SoCal), Upper East Side (NYC), Buckhead (Atlanta), and GCC (Greenville) they were able to program and cut keys and we’re about $200 cheaper than the dealer…yet other parts of town told me to go to the dealer….not saying that’s always the case, but in big cities it’s seemed to be when the locksmiths have more volume and the ability to invest in the programmers…