I wanted to chime in and recommend checking out photography experiences on AirBnB. I have done a few of them around the world during solo travels and have always gotten great photos back. I just took a quick look for photography portraits in Venice on AirBnB and there are some really good ones! You could send them a message and mention your proposal, and they will likely be able to create a custom session for you.
I have never used Flytographer, but I know people who have for family portraits and they raved about the service. The only downside is that I feel like Flytographer has gotten really expensive (they recently increased their pricing), and sometimes, you can find equal talent for a better price on AirBnB. I don’t want to devalue artists like photographers, of course, but I always recommend just really looking through photographer profiles and making sure their style matches up with what you want to make sure it’s worth it since they do tend to be a bit more expensive.
You can also search Instagram with hashtags like #venicephotographer, and I’m sure you’ll find some great ones :) You can message directly on Instagram and ask about pricing, etc.
Keep us posted how it works out for you, and good luck!