Tent and Zipper repairs

Some years ago, my wife and I purchased a Natural Instincts family dome tent.
And we have been very happy.
It base seen a lot of rain and mud and South Africa.
But not we have a problem. Now one of the zips on the inside sheet in the door is not working and we have also done a home repair on an exterior zip. The exterior zip now only has an exterior pull which makes it difficult to open from inside.
There is no local support from the reseller and I am battling to find anyone willing to repair tentar not made from canvass and PVC.

Are there any recommendations for a repairer in Gauteng ?

I cannot understand why manufacturers skimp on zips.
I would gladly pay an extra 2 or 3 hundred Rand for good zips in both tents and bags and trousers ( YKK especially) than have to let a good product go when the cheap rubbish fails.