I use a simple Bitubo shock. Can`t say anything bad about it. It was the cheapest replacement i found a couple of years ago. For me it is a little bit to hard, but the spring tension is easily adjustible.
The only "problem" with this shock is that the rebound adjustment lever is on the bottom. The lever is a little bit too long and touches the shock leverage. As this is just a screw with a plastic cap on it`s head it`s easy to remove and shorten it. Just be careful to make a mark wat which position the adjuster exactly was when you remove the screw so you get to the exact same position when you reassemble it.
After about 4 years the paint of the shock is a bit bubbly and coming off on top. Maybe this is because of low paint quality in combination with the heat from the rear header, I don`t know.
Anyway I think it`s o.k. and as the price is only a part of what the original new part costs it`s even better
Onve in a while you`ll find an original shock on ebay.
Check ebay.de there was one a couple of days ago.
Gerhard