Agilent part number 85024-60011. The plastic tip is broken off from the one I have. Agilent is asking for 122Euro + VAT which seems really steep for such a part.
Looking also for a reasonably priced Probe-tip-to-N adapter 11880A for 85024A/54701A/1152A, part number 11880-60001.
If somebody needs I have one extra 10:1 probe tip 10241A for 1120A - 25Euro + shipping.
73, Jaakko