They exist for 12V fans, but at 5V it's super niche.

The only viable option I see is to build it yourself using an Atmega328P based microcontroller and a thermistor, or other temperature sensor.

This is an example of the microcontroller: https://www.amazon.com/dp/B0BGJBZV9T

It's basically a tiny computer that you can program to do whatever you want. It takes USB for both power & input.

It has 5V output and a ground so the fan can connect directly to it.

It can be programmed to output a PWM signal, read the fan speed, read various kinds of temperature sensors, work with various knobs and buttons, and even touchscreens.

You can use the Arduino IDE to program it, and ChatGPT to make the code. You can probably find similar Arduino based projects with code already published if you search online for "Arduino PWM fan controller".

Something like this is a pretty comprehensive kit: https://www.amazon.com/dp/B0BDR2P5CZ

You get an LCD screen, keyboard, breadboard, jumper wire, and a bunch of breadboard friendly sensors including temperature and humidity.

You can easily connect everything with a breadboard and jumper wires. You can push the jumper wire into the fan connector.