Well with some spec sheet reading:
This looks useful:
http://www.farnell.com/datasheets/1903291.pdf
@$16 ea.

Feed it a logic signal and it will sharpen up the rise/fall to the sub 40 ps category with 50ohm termination built in. 400mV p-p
80ps min PW.

Questions I have:
1) Would this be a viable alt to the tunnel diode Tr bandwidth checking?
2) With an OXCO driven clk, would this be an alt to a time mark gen for cal purposes?