I had a look on the HSE web site, thinking they would have a pdf still available, but unfortunately not. If you are collecting booklets, that is of no help, but if it is just the information therein that you require, going to the hse.gov.uk web site and putting "quarries shotfirers" without the quotes in the search box will lead you to lots of information which may or may not tell you what you need. But you have probably done all that already.
The booklet may predate the web site, and never have been scanned in, but it is unfortunate that documents which people may still want to refer to do actually disappear. Regulations change and some junior person sees that it no longer applies and throws a box of them in the skip.
The HSE is as good as anyone else in that regard...