home brew isolated oscilloscope lead
Another choice is if your have a multi input 'scope, take two leads, connect their grounds leads together (and tape if needed to prevent shorting) and then use one as "signal" and the other as "ground" and use the A + (inv. B) functions of your scope to measure the signal and to remove the ground signal.  It means you use more leads and can interfere with some scope functions.  BUt it's another choice for you ...