During my journeys I noticed that "wall wart" power supplies and travel adapters don't go very well together, especially when the wall socket is a worn out NEMA 5 one. The power supply tends to fall off very easily and wears off the wall socket even more. That is not so much of a problem with adapters for BS 1363 (UK) sockets, but often there is not enough space between the socket and a nightstand for the cascade of adapter and wall-wart. But as I always carry a bunch of C7 (figure-8) cords for the respective country, a C8 connector to euro plug receptacle adapter cable would be helpful (and lighter and smaller than most travel adapters.) Unfortunately, only the opposite seems to exist: I found plenty of euro to C7 plug adapters. So I had to build my own. I bought a euro socket and a C7/C8 extension cord. From the extension cord, I cut off 30 cm of cable on the C8 side (the one with the pins), mounted the euro socket on the open end of the cable, and there we have our pigtail adapter:
No strain on the wall socket, no clunky adapter, leightweight, and no special parts required. If you want to rebuild it yourself, obey electrical security regulations and best practices to avoid risk of electical shock and fire hazards.