You can easily make a 50kV probe for free (surplus/scrap junk yard) or
Depends on your Probe Load R specs. Typ. 1000:1 probes are designed for 100 M, which you can make with a string of 500V or 1kV cheap resistors inside a polycarbonate tube with polycarbonate hand shield.
Using rubber wire tip >10cm from hand position
Alligator clamp for ground to Blk wire.
But all sources of grid power at >=600Vac have Arc Flash minimum distances with fire protection gear , so,I trust this is not your goal.
I have measured 200kVac using a very large size low pF Cap transform to low voltage. This works better than a voltage transformer.