I can't seem to find any on eBay, my local ReStore has no HIDs, and nothing is helping online. Where do you find them?

I've found that searching bulb codes (like HR175DX39 for a General Electric deluxe white 175 watt MV lamp) shows replacement bulbs.
As for mercury luminaires, searching brands up can yield results that are interesting. Try "GE luminaire" or GE Street Light" or similar terms.