Hi and welcome. You can guarantee when you do finally sniff one out and purchase one; at least two will appear closer to home and arguably more suitable.
From my many hours wasted being an early Polo owner over the last 10 years; I can say these cars are an enthusiast car. Combination of marmite 90's looks, relatively crude suspension setup and lack of big engine compatibility has meant these cars have never gained the desirability of a car such as the mk1/2 golf gti. Most people can spot a golf; but would have no idea what a Polo G40 was. Thus the price has never matched the rarity of these cars. As a consequence many have been broken/scrapped or reshelled due to the lack of value to the chassis. An example recently; Jezza was advertising his highly specced original G in atlas grey (nice colour) for a price that was a total song.. I'm not sure whether he sold it in the end, but he certainly didn't have his arm bitten off for the complete car. In fact I bought the exhaust; which probably answers that one. So in many cases people just break the car for the value of the individual parts and play the long game. Which reduces the chances of G40's being for sale years on.
Had these cars had the following of other icons of the past; many shells may have been saved. However the amount of guys I talk to who tell me of all the classic fords they've raced/stripped and crushed over the years I guess this isn't always true. But they probably wouldn't have just broken a lotus cortina or a mk1 Mexico, which I suppose the G40 would be similar to in terms of "special" model. Their fate is driven by value unfortunately and even though they're probably a rarer car than a mk1 golf gti they don't command the same money. Finding a completely standard concours car Would be a tough job. I expect they do exist and really are worth top money for the fact they're standard and unmolested.. to the right buyer.
If you're a hands-on guy though you probably don't mind something which needs some careful nurturing and putting back to standard perhaps.. this can be quite satisfying (albeit often expensive). £3-4K might get you something decent - as and when someone has a change of circumstance/heart and decides to sell.
Every time I search for them; I struggle to find something good. Keep checking in the for sale section and on the usual eBay, gumtree, car and classic etc. Best of luck.
A point worth noting with regards to the true polo enthusiast; it doesn't really matter if the shell is an original G40, as long as it's rust free and has all the goodies lusted after to bring the dream to life and make a true giant-slayer.