My original list of alternates for buck converter ICs included both the 3Peak TPP361061 and TPP361063. These are 2.2MHz synchronous buck converters with impressive specs at reasonable prices. I soldered the TPP361061 into the buck converter daughter board first. What makes this switcher a bit different is that it uses pulse skipping mode (PSM) at low load currents to keep the efficiency high. The problem is that it would be using PSM with the current levels that the probe uses. The output ripple is not that bad, but it isn't that good either (output load = 82 Ohm):

I measured the efficiency at around 84%, no better than other ICs operating at PWM. So I eliminated this part from consideration.

I then soldered its cousin, the TPP361063 in its place. This is a forced PWM converter...no PSM. When I powered it on with no load the input current indicated it was drawing 10mA. It should have been less than 1mA. Output voltage was correct, but the switching waveform looked a bit wonky. After playing with it a bit I eventually destroyed the only part in my possession. So that one is off the consideration list as well. I did not do anything to the component that I would not normally do to solder it into place. As far as I'm concerned the part was defective when I received it from Digikey, and for $0.50 it is not worth messing with.

It's OK if you want to use TPP361063 in this application, let me know how it performed for you.