We have several options that will fit into your $300.00 budget. I think the biggest question is if you need to vent the light or not? I’ve put a couple of options together below:
XtraSun HPS Ballast, 600W = $141.95
Standard 600W HPS Bulb = $53.95
XtraSun Reflector (no vent) = $65.50
XtraSun 6 Reflector (w/ vent) = $84.95
https://www.planetnatural.com/product/xtrasun-high-pressure-sodium-ballast/
https://www.planetnatural.com/product/high-pressure-sodium-lamps-hps/
https://www.planetnatural.com/product/xtrasun-6-ac-reflector/
If you want to go digital, I suggest the Hydrofarm Special (Bulb & Ballast Combo) for $266.95 with one of the XtraSun Reflectors.
Hope this helps!