Speed Control from the Grace Company, I have one on my Viking Mega Quilter (not the 18x8)
Plugs into same spot where foot control plugs in, and control is attached to handle on carriage.
https://www.graceframe.com/en/product/speed-control
dial controls stitching speed when turned on, not a regulator. Pulse button starts stitching and continues while button is held down. On/Off button starts and stops stitching, does not have to be continually pushed.