All the dealers say they don't have it. Not in the US or Germany. The first twenty organic google search results all say they have the part but, when you call or go ahead and buy the part online, they do not have it.
Everything I've heard on 126 is that they're "single use". So you wouldn't find a used one. I need one in probably the next year for my SD, but fortunately not for a while on the SEC. Maybe MB will do a run of them.