If you're not prepared to pay what people are asking for in Classified ads (remember always worth asking their best price), then i'm afraid you'll need to do more legwork than firing up a post and expecting offers of cheap ones to come your way.
That means getting out there, looking in scrapyards, messaging breakers on ebay etc etc etc. You'll probably quickly find that it would have been easier to just buy the advertised one by the time you've looked in 10 scrappies, (paying the petrol to get to them) taken off about 30 cam covers to see what's inside etc, or a breaker does their research and asks either a high price or high postage.