So Just a quick update I did print out some adapters for the cheap probes and they work great.
Good job, and a neat way of avoiding having to mentally shift the decimal point!
Now I suggest doing something similar for the
other end of the probe - so that you can get a
much better trace on your scope with high-speed digital signals. That's vital if you are interested in the signal integrity of "digital" signals and/or want to see glitches and relative phases. ("digital" since all signals are analogue, even if they are interpreted as binary).
Objective: get rid of the 150nH inductance in the 6" ground strap plus croc(k)-clip. With a 20pF scope tip capacitance, when hit with a sharp voltage transition (e.g. TTL/CMOS) you will see significant ringing at 70-80MHz, which will be clearly visible on a 100MHz scope as a 20% overshoot. See the end of
http://www.dfad.com.au/links/THE%20SECRET%20WORLD%20OF%20PROBES%20OCt09.pdf for examples.
Usually probes come with a short wire spring that slips over the end of the ground sleeve and contacts a nearby ground plane - which is fine if there is an accessible ground at exactly the right distance from the point being probed. But professional high speed probes use a "bayonet", e.g. see the attached picture of an old HP probe. That example is mostly metal, but that isn't important - I have a 1.5GHz Z0 probe where the bayonet support is mostly plastic.
Consider connecting the swivelling bayonet to the probe ground using thin phosphor bronze sheet bent into the right shape (sheet = lower inductance, phosphor bronze = springy). I find pogo-pins are too fragile for the bayonet: use a nail or maybe a sewing needle.
I suspect UV-cured resin might be more rigid and finer resolution than typical 3D printer plastic, but I haven't tried it.