Luckily, after searching for a while in my “old power supplies box” (a box where I store all the old phone chargers and power supplies), I found two chargers for old Siemens phones, having the connector that I needed. However, I quickly realized that they only had the VCC and GND pins and I needed a connector with Tx and Rx pins too.
After putting the pins inside I had to find a cable with four wires to solder them to the four pins. I ended up using a damaged USB cable that I had laying around and removed the USB connector. After soldering the four wires I filled the inside of the connector with hot glue and closed the housing of the connector.