I Googled PC Specialists competitors today and they all have the SM961 in stock, so fingers crossed PCS get them back within 30 days as clearly they still exist. I also saw them being sold as individual components online.
I did the same but I suspect that they don't have any in stock. I rang an online parts suppliers as well this morning as it was showing as in stock with them but when I spoke to them they didn't have any and had no ETA.