You probably already know that you will also need to have the Lens Control S to operate the shutter.
I would also advise you to buy the adaptor to allow you to use the Lens Control S plugged to the mains, as the rechargeable batteries are very old technology and don't last long.
The adaptor looks like a dummy battery with a cable coming out of it to a 6 Volt DC adaptor, all supplied together.
You are always advised to buy the shutter together with a lens, as they then come calibrated by Rollei (sometimes they place very thin sims in the lens threads) to offer the best optical alignment. But I've bought them separately too and I haven't really noticed any difference.
I've bought some of mine from Robert White in the UK. I've also bought quite a few from my very favourite and most professional supplier in the UK:
www.linhofstudio.comRollei tends to be one of these firms slow in supplying and repairing, so sometimes there is some waiting to get some, but you may be lucky.
The shutters themselves work reliably well in my experience, I've had mine since the very outcome of digital photography and they are still working well every single day.
The Control S, however, is a relic of bad design that should've been completely updated 10 years ago. But it does the job.
Edward