The thing with those coil shocks is that the dampers don't seem to like spending most of their life wiggling up and down in a narrow part of the range of travel, and soon end up in a state where their primary function is to make hydraulic squelching noises. The effect of the lack of damping is of course a net increase in rattliness.
After getting through a couple of them on the Streetmachine, I gambled on the one air shock I could find online in the appropriate unobtanium size; some middle-of-the-road Fox thing. I'm underwhelmed by the frequency with which it requires topping up (compared to the fork on my mountain bike), but the improvement to the suspension has been dramatic. The simplicity of jibbling the pressure to suit the amount of luggage carried is a useful bonus, too.
Should that fail, I will suck it up and see if HPVelotechnik will supply an appropriate DT-Swiss offering. The exchange of limbs for extremely competent Germans efficiently supplying obscure components is already proven to be worthwhile, compared with the usual blood-from-stone process of going via a dealer.
