Try searching for violet or white BS EN 60309 sockets, or "!2V sockets". Most are described according to their intended voltage rather than earthing system or degree of separation.
At lower power levels, phone chargers laptop computers, led lights, there is very little distinction made, and where there is it is more about locking you to the maker's own standard - I have 2 power supplies for this laptop, made it different years, one is PELV, in that the negative side of the output jack is earthed, so if mains tries to escape down the thin end of the wire, the fuse should blow, while the second has a 2 core mains lead and is in effect SELV - i.e. double insulated internally to the PSU. The connectors on the ends are the same - being for the same laptop, but jut enough different from every other one in the house to be not quite interchangeable. The USB outputs built into the wall sockets are also earth free and SELV, but on the desktop machine again the negative side, and the shell is earthed, so may identify as PELV.
You cannot even use the 2pin/3 pin thing to distinguish, as when one side is grounded, there are still only 2 pins.
Functional ELV is rare, and usually bespoke rather than connecting kit from different makers, so things tend to be hard wired, or like interlinked smoke alarms, on a custom base.
The attached MK Commando Plugs & Sockets Catalogue linked to below shows examples of BS EN 60309 plugs and sockets for use at ELV. The colour-code is violet for use at 25 V 50/60 Hz and white for use at 25 V / 50 V DC.
For other applications falling outside of the definitions in BS EN 60309 it is often a case of ensuring that the plugs and sockets used for ELV are clearly identified and are incompatible with any others (particularly those > ELV) in use in the same installation.
