Very simple holder for hydrometer that uses 2 sets of magnets to hold the bottom and the back firmly in place. This design is thicker and stronger requiring 5x2mm and 10x3mm magnets. I use mine in the back of the printer so that I can see it via the built in camera of the X1C. I print with 10 walls so it's solid, feel free to change as you see fit.
Used these hydrometers: https://www.amazon.com/dp/B0CJM5R5N6?psc=1&ref=ppx_yo2ov_dt_b_product_details