Try Demon Tweeks in the UK
https://www.demon-tweeks.com/uk/vdo-dip-tube-type-fuel-sender-for-vdo-gauge-389218/ Not the cheapest at £103, they were less than £50 not long ago. Anything longer than the 280mm will not fit.
Wilson, you should be able to do 300km between fill ups easily. I cross check the gauge (mine is almost believable!) to the odometer and 200 miles is fine with usually something in the mid to high 20's litres at refill. If the indications are really random, remove the sender unit and take the cover off, carefully. You can gently clean the two fine wires with some very fine abrasive and that often restores the steady(ish) indication. I find this works for about two years before another clean is required. Maybe something to do with me not using the car over the winter months and surface corrosion on the wires?
