WTB Montblanc Mesiterstuck 149 cap clip

[kuli1961]

Want to buy a cap clip for MB Meisterstuck 149, as older as possible, because the fp is dated somewhere 1960-1965. O ring's measures on the top of the clip are:
outer diameter -cca 15 mm, inner diameter of the ring - cca 11,5 mm. O -ring's edges are (preferably, should be) slightly rounded.