Ive been trying to find some street lights to add to my property because I love the look and color. Im hoping to find hps/lps or mv lights. I looked all over online but couldnt find any used fixtures. Is there any particular place to look that anyone knows of. Any help is appreciated

You may try to ask the organization maintaining the public lighting in your area, to buy a retired post after some upgrade. Not guaranteed whether they just wont send you away, but you may have at least some small chance.

If you're in the US/Canada there are generally a few listings for used and new in box streetlighting luminaires on eBay. Generally they'll be high pressure sodium but mercury vapour and metal halide units sometimes show up. They can easily be reballasted for any given voltage, light source, and wattage if you're comfortable changing the ballast.

If you rather go a different route, try checking your local online classifieds (Craigslist/Facebook Marketplace). Sometimes they show up at the Restore, antique and flea markets, and rarely in thrift stores. You could also try asking around at any local lighting contractors, utilities, scrap yards.

Say I were to find a hps fixture online. Would i be able to convert it to mercury vapor or would I have to buy a ballast. I hear that they dont make them anymore.

U can still get them MV ballast on Ebay.

You don't have to change out the ballast when changing from SON to MH.
As long the wattage of the ballast is the same as the bulb, it should work. The igniter also doesn't need to be changed over either.

Say I were to find a hps fixture online. Would i be able to convert it to mercury vapor or would I have to buy a ballast. I hear that they dont make them anymore.

Say I were to find a hps fixture online. Would i be able to convert it to mercury vapor or would I have to buy a ballast. I hear that they dont make them anymore.

You would have to buy a ballast unfortunately, unlike European HPS lamps, North American HPS lamps aren't that interchangeable with MV or MH. Special conversion lamps are made for 250w and 400w HPS but they are hard to find. New old stock MV ballasts can still be found on eBay and you can run the same wattage MV lamp in the 175-1000w range using a probe start MH ballast of the same wattage.