Old plastic guttering problem. Help!

My folks have an old 4" plastic gutter servicing the flat roof of their kitchen extension. There's been a leak (only during very heavy rain) for a while now from the external stop end which this morning decided to give up the ghost and fall off. One of the clips has broken off and the gasket has perished (probably the cause of the leak). I've looked for a replacement stop end on the usual websites (wickes, b&q, screwfix) but they are all of the 112mm variety (4.4") which obviously won't fit.

Has anyone any advice on where i can find one that will? What metric size size should I be looking for (100mm perhaps)? Do they just not make them any more? Or is there some workaround I could use? I really don't want to have to replace the whole lot as there is nothing else wrong with it.

Any help gratefully received!

sounds as though the gutters are past their sell by date!
the rubber seals have rotted and the pvc has become brittle with age.

anyway you can stick the stopend back on with some silicone which should last until something else drops off

Not the answer I wanted!

You're probably right, I should replace the whole lot

I've just started putting a new bathroom in at my place and I could have done without the extra hassle. I'll probably just stick it back on with mastik and fix it properly later in the summer.

Cheers.