I can't say if I have seen a W113 with an original MB warning triangle, option 226. However, I found a warning triangle from an early W107 for the boot of my 1970 280SL. I would assume that these triangles were not updated from the W113 to the W107. These were required to be in your boot by German government as of April 26, 1966. The manufacturer is WEGU, Amtlich Zugelassen Pruf - Nr. (part number) K 13702. It is in a red semi-hard plastic case 43cm long. Triangle is red plastic reflector with a pull-up while plastic film (!) on a steel stand, and folds up into case.
It would be interesting to see if anyone else has these in their W113 boots. I show my SL and this is a great touch for showing the boot.
Bob