Pentax (K or Screw) or Olympus, I did have a 85mm Jupiter-9 but stupidly gave it away a few years back when they were cheap and plentyful.
In that case, I would look for an M42 105mm f/2.8 Takumar on E-Bay. I sold two of these at work in literally near-mint condition with original caps, filters, and cases, and they went for about $75 a piece on E-Bay. Less pristine ones would go for less. I could kick myself for not grabbing one of them! I got the Spotmatic body, 35mm f/3.5, and 50mm f/1.4 in similarly pristine condition, but since the 105s would actually bring some money, I told the boss that we should sell them.
Not an 85, but close, and definitely within your budget with some patience.
"Truth and love are my law and worship. Form and conscience are my manifestation and guide. Nature and peace are my shelter and companions. Order is my attitude. Beauty and perfection are my attack."
For cheap: forget ebay or any site on the internet.
Many people think that old means value.
Check your lacal camera stores, talk with them and tell them what you are intersted in at what price, leave your telephone number.
Many camera stores will take trades when selling a new camera......