The QL part of ebay remains buoyant with 4 pages of items. There is a QL offered as a buy it now for £70 including p&p. But before anyone rushes to a bargain it is described as "don't know if it is working". So £70 for spares is expensive.
More usefully there is a batch of books for sale including Andy Pennell's guide to the QL operating system. Titled "The Sinclair QDOS Companion". This is one of the 3 essential books that QL Heaven has used over the years to achieve programming results. The insights into the QDOS/SMSQE OS given in this book are essential if any understanding of the secrets of the OS is needed to achieve programming results. It does not matter that this book was originally published in 1985. The info in it is still relevant especially as a rump of Quanta membership still adhere to original black box QLs running QDOS and SuperBasic so any current program that intends to be backwards compatible needs to understand and obey the OS rules described therein. In addition for more modern systems like QPC2 smsq/e is more backwards compatible than Windows has been up to Windows 7 so the book is still more than useful.