Enginge bay rattle on passenger side - advice

[aliasofmike]

I've been doing research regarding a rattle that has presented in my girlfriend's 2007 Toyota yaris (1NZ-FE). The car has 104k miles, and the rattling was noticed just recently. It appears to be getting worse.

It seemed like the most common problem was with the water pump. I've taken a look at it, and I don't notice any pink residue, and in general the pulley seems in good repair. I wasn't able to get a great look at it.

The other possibility I am considering is that the noise is coming from the A/C assembly. I found less information on diagnosing this, and I'm not sure where too look. The A/C still works and the noise doesn't increase when the A/C on, fwiw.

The noise is apparent while idling, and increases with RPMs to a point.

It is very hot weather here, and were planning on taking a day trip tomorrow. If it is the water pump, I'm concerned that this would be a gamble/bad idea.

Any advice or questions for me to follow up on, much appreciated.