Fortunately, some of the most useful probes are ones you can replicate at your bench.
Near field probes for magnetic (H) field are easy to make from coax or better, rigid coax. For electric field, E field probes are also easy to make, generally a short exposed center conductor coax.
Be sure that what you make is well insulated so you never need to worry about your analyzer's front end or that of a preamp.
At first I thought you wanted scope probing on a spectrum analyzer. Apparently not but if the need arises, check out the old Tektronix 1103 power supply and Tek's active probes. They are fairly priced, unlike Agilent/Keysight probes. The 1103 can be used forever, having a BNC output to anything you want.