Where to buy one Apple European plug with USB C and A outlets for France and Italy?

don't believe apple produce any ac chargers with both c and a connectors

belkin does though

Belkin BoostCharge Dual Wall Charger (42W) - Apple

would expect anker would have them too

all modern chargers work with 110volt to 240volt so only thing you need to use them in countries with other plugs is a plug adaptor

To start with, both France and Italy typically have Type C outlets. In addition, some outlets in France are Type E or Type F ... so having only one electrical plug adapter will not work at all locations in both countries.

As far as, having a power adapter that provides both USB-C and USB-A ports may not be easy to find. There are some, provided by Apple, that have two USB-C ports and you could use this with a USB-C-to-USB-A adapter if necessary. Here is one example: 35W Dual USB-C Port Compact Power Adapter - Apple. Apple also sells the World Travel Kit with multiple plug adapters.

Is this power adapter to be used with just your iPhone 15 Pro, or with other devices, like a Mac laptop?

Then the Apple power adapter I provided you a link for should work for you. It has a removable "duckhead" that will allow you to change the electrical plug for which country you are in. These are provided in the Apple World Travel Kit. The only other thing you will need, as I mentioned, is a male USB-C to female USB-A adapter. The male end would be inserted into one of those two USB-C ports on the power adapter, and then, you could connect your USB-A charging cord to the adapter's female end. You should be able to find them at places like Amazon.

Apple also sells these.

You can buy an Apple World Travel Adapter Kit which includes plugs for Europe, including France and Italy, and has both USB-C and USB-A outlets in one adapter. It's a convenient option for traveling light with just one plug that works in multiple countries.