I understand your reason for looking at dealers cars to get the p/x but at the money you are looking to spend it is unlikely they will ever have a good example as you will normally find advertised on specialist forums like this one.
All very obvious, but when you then take into account the trade-in price on your p/x, the dealers profit (aside from any work he has to do on the car before sale), unless he is really desperate to make a sale at those s/h price levels you are looking at for a ZED, then I can only wish you luck.
But you really ought to think about privately selling yours, at say the money you have been offered by the trade. Some reports back about "we buy any car.com" are less than encouraging but then others have found they got more than the trade would give But it will then leave you with a budget to buy a really cherished example on here or another specialist private sales area. If you need wheels 24/7 and don't have others you can use in between selling and buying then I fully accept that makes life difficult, but thats when a reality check has to step in.
When buying new/nearly new the margins are usually more flexible for the trade, in my experience, and of course you don't get the wear & tear issues the beneft of drive in the old and drive out the new. That time will come for you.