Yes, I had a digital noise generator in mind. It is a rather simple circuit.
The HP 3561A (and later models) dynamic signal analyzer has such a source, and uses it for various measurements. HP3561 only goes up to 100kHz, but with modern chips, 10MHz would be easy.
10MHz is in the "oscilloscope range", so you are not limited to GHz techniques. Of course, you could also make a (zener) diode noise source and calibrate it (after some amplification) with a HP3400, or a modern scope, with built in RMS calculation. Exact amounts of amplification up to 10MHz are also no problem with modern chips.
Most modern AWGs can also produce noise at least up to 10MHz. You would need some attenuation to get down to HP364 levels, but attenuation is also easy at 10MHz.
