You are right about 165 80R 15 being the correct size for VW beetles. However it is no more available. The last consignment of NEXEN's we got from karachi is probably sold out or if there are any left they'd have a years life left after sitting on the shelves. The next best option is Eurostars 175 65 15 which come factory fitted on a Honda City. Most owners do not like the looks and performance of Eurostars as there were a few issues on the motorway at high speeds. However with proper inflation and care these perform flawlessly on our VW's. the only thing visual that I do not like about them is that they leave a lot more empty space under the fenders (as they are lower profile than stock) The engine would run at about 150-200rpm higher at 100km/hr compared to stock size and the speedometer would be a tad out as well. However this should not be a major concern for city drivers.
As regards the correct size tyres, we have a huge source of these tyres right across our border..India. This size is correct for Ambassador and is produced in plenty. I brought a pair of tyres from India and was quite pleased with their performance. The roads in India are worse than the roads here and the weight of an Ambassador is comparable with our VW's so they are a perfect solution. JK tyres are manufactured under licence from Continental tyres AG. There are other brands available (same size) so its a question of getting them here. If someone can speak to an importer we can order 10 or so sets in the first instance with a promise of repeat orders. We tried the JK tyres dealer in Lahore and he turned out to be a dud..didn't seem interested in a small order. However i am sure there is some enterprising dealer who might want this small but steady business...