OT:
Although not all that one might want for calibrating scopes, a good start would be a reasonably good Rf signal generator, not necessarily PG or SG modules ...
Some sellers on eBay appear to consistently have "tested" (synthesized) Rf signal generators that go up to 1 or 2 GHz,
at reasonable prices. They often show photos on a spectrum analyzer of their RF signal generator in operation, as proof ...
For example { although there are many others } : EDIinc
Likely a better place to start than a vendor who shows no such photos...
