Funny enough, I've just ordered the official repair kit.
Opted for that because it pretty much makes it a brand new valve for a little bit more and guarantees the correct parts.
Rootek you get 3 kits for £19.75 or 5 kits for £24.75. All stainless springs plus opening tool. The Rootek spring works better than the original spring too.
It is an interesting topic.
I have 2 univalves on my poles that are from the original batch and they are still working fine. The only issue was the the small o ring in one also came dislodged. I glued it back.
They are also prone to sticking, but a bit of silicone grease around the large o ring cures it for another couple of months.
Saying that, we still have a working pole on the van with an Aquadapter on it. In the past 5 years I've just replaced the spring once.