Oh dear, thats not good, being without water.
Unfortunately, I do not think you can force your neighbour to allow you to bring a water pipe through. Our neighbour had the same problem with his well drying up during the summer, but he was able to bring mains water in to solve his problem.
You have gone down the bore hole route, without success, so to be honest I cannot see any other way round the problem than what you are doing, which is bringing water in, in bowsers.
Is there any way you can catch rain water in large quantities and store it in tanks?
I do hope you can find a way round this.