The subpanel wouldn’t be permanent, build it on a board with a dryer cord going out. That way you can plug it in anywhere you move with a dryer receptacle.
Horticulture Electronic Dimmable 1000W Watts MH HPS Digital Grow Light Ballast...
1 x Electronic dimmable 1000W digital ballast. 1000W BUNDLE KIT. DOUBLE ENDED REFLECTOR & SYSTM. DIGITAL BALLAST. Built-in cooling fan to run cooler than other digital ballasts. 1 x heavy-duty grounded power cords (3-prong 120V plug. ).