Adding to the list of possible Options...
The best injection site is actually directly into the Accelerator Pump Carb Injector Ports or Tee-ing into the Accelerator Hose.
Seadoo Fogging Kit # 295500899 was made for this purpose.
"It consists of a "T", a One-way Valve, some Hose and Clamps. And instructions.
It T's into the accelerator pump hose and uses the accelerator pump nozzles to squirt seadoo lube down the carb throats. You will have a clear hose emerging from the carbs with a red squirter tube that you plug into your seadoo lube can. Iy makes fogging rediculously easy."
A Primer System could also serve the purpose, as mentioned before. Would need to pump Pre-Mix or Oil.
As far as the ideal location for the Air Box Fogging Port, you'll have to determine that.