The BeachTek DXA-2T mounts to your camera tripod. Your camera then mounts to the top of the DXA-2T. It allows for external microphones with balanced, low-impedance XLR outputs, to be connected to the stereo 3.5mm stereo input jack on your camera.
The DXA-2T is a passive device so it doesn’t need a power supply. With gain control and various switches to isolate earth, etc, it’s an amazingly simple but versatile solution.
The user manual (and specifications) are available here: https://beachtek.com/wp-content/uploads/2018/03/DXA2TEnglishManualV02.pdf
PRICE: £85.00 plus £10.00 p&p to UK mainland. Cost of shipping includes insurance.