What you are looking for is pretty much the holy grail of Land Rovers.... a solid, mechanically fit, patina'd, original car with a canvas, o/d and freewheeling hubs! That is what everyone else is looking for too, so you will need to be prepared to move quickly and dig your hand deeep into your pocket when the opportunity presents
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That may require a re-assessment of your budget.... The cars in high demand and low supply do command the highest prices.
They are out there though and do still come up for sale privately through the usual channels and here, so it's worth keeping on scanning. The commercial sales outfits also have a decent knack of rooting out cars like the one you are looking for (as they know they sell well!) but you'll have to pay their rates and you aren't guaranteed a better car at the end of it.
As others have said, getting involved with your local club will be worthwhile - you can sometimes buy cars that aren't officially for sale through making contacts and talking to people. The other thing worth considering is buying a 'near-enough' car and making into the car you want. Of your stipulations, the only thing that can't be genuinely replicated is the patina... so if you were to find a car with the right patina, but nothing else, you can make the rest of it fit your desires with enough money. I wouldn't rule out a hardtop car as it's so relatively easy to convert to canvas. The mechanical aspects can also be brought up to spec pretty cheaply and easily. A car with a rough chassis can have the chassis replaced with a galvanised which will also improve it's long term desirability.... It's worth thinking more liberally.
Free wheel hubs and overdrive wouldn't be a deal breaker on anything for me, as they are so easy to fit after purchase.
As with all these things, it really depends on how much money you want to spend and how patient you can be