You can buy a good and cheap voltage regulator aka dimmer from a chineese internet store for your household light/vent speed/other control but usually they come without a case or with poor one. I did my best to design a good one. It fits perfectly this dimmer: https://www.aliexpress.com/item/1pcs-2000W-thyristor-AC-voltage-regulator-high-power-electronic-for-speed-control-dimming-thermostat/32819974059.html?spm=a2g0s.9042311.0.0.27424c4dUr6VkK and many others of the same opensource design.

Features:

• easy to print, no supports needed;
• side holes for the wires are reduced to keep the surface nice and clean, Just enlarge the holes with the drill to suit your cables;
• ajustable in all directions before you tighten the screws;
• uses some vent holes for heatsink inside;
• all the dimensions are optimized for 0.4 nozzle 0.2 mm resolution.

Please turn on "enable bridge settings", enable ironing and set all the patterns to "concentric" in your slicer for the best result.