I know! Just two days ago, before I found the original that was in the case I had stored away, I was using one from a big set of keys I got at Pep Boys or Auto Zone. It was the smallest one in this big set of keys (English, not Metric), and it was marked .050. BTW, the trem key is 3/32.
Side story - Many years ago I worked for a company called Weber Aircraft in Burbank Ca. I couldn't adjust my bridge, so I thought I'd sneak out of work, drive to Fender in Fullerton and see if they could sell me a new bridge. One of their guys took a look at it and determined the hex key was bad or worn, and just gave me another.. problem solved. About 15 years later, Weber Aircraft was moved to Fullerton. I hated the commute, but the building looked awfully familiar. You guessed it, Fender had also relocated, and I was now working in the old building that CBS had build for Fender. š I still hated the commute š