I'll second erics take on Swagelok stuff. Their small diameter tube fittings are good for gripping stainless sheathed thermocouples. Another good source for BSPP fittings and adapters is Parker Hannifin. The Tube Fittings Division catalog is a good place to start looking for European fittings and adapters. This catalog has a wealth of information on almost any threaded pipe fitting you will find in an espresso maker.http://www.parker.com/tfd/cat/pdffiles/open.pdf
BSPP is very common on European industrial equipment. The threads and how the fitting seals is unlike anything else in common usage here in North America; you will not find them in any hardware store. In my experience European equipment can feature a mishmash of fitting types. I once worked on Swiss die casting machine which, in addition to the usual metric threaded stuff, featured 2 varieties of British pipe threads, two different SAE fittings, and one oddball (non-ISO) DIN fitting. If you are doing some machine plumbing modifications you may want to look at the Port Details section in the aforementioned Parker catalog. Case in point, the tapered pipe fittings you see in your machine are probably BSPT, not NPT. I've seen people cram the two together but I'd avoid doing so with high temperature pressurized water. The good news is that as Parker swallows up manufacturers worldwide they have become a one stop shop for European spec fittings and valves.
Whether you get your fittings from Swagelock, Parker, or whomever, be prepared to pay an inordinate amount compared to your local hardware store. These are high quality industrial fittings, the same ones your machine was built with, and their cost is part of the reason why good espresso machines cost as much as they do.