Have a look at this;
Either NTK (NGK) or DENSO would supply the original sensor, there are instructions on how to test them (old school analogue multimeter is handy for this) but if you do need a replacement check the number of wires the sensor has and the colours of the wires, this will help identify the type you need. The best bet is them to look though the NTK catalogue to find an OE equvalent.
This is the only Daihatsu part listed, it gives you an idea of the number of wires connector type and lead length. Have a look through the toyota ones and maybe some of the Suzuki ones too. You nay have to swap the connecotr over from your old one.
the thread size on all of them seems to be the same - cant remember what it is offhand but the sensor will need a 23mm socket.
it's the number of wires that make them different (1 - 5) if the the jbjl and the efrl have the same number of wires then the odds are it's the same sensor.
the lambda on the jbjl seems ridiculously small. Fit a 14mm socket over it. It is a single wire like the efrl but the size seems completely different. Ah Daihatsu, you love making life interesting...
here's a link to one used in japan. So tiny!
Might have to go with legitimate daihatsu. Sigh.
Funk, are you sure thats the lambda sensor with the 14mm head and not the heat sensor for the cat, which is also single wire.
The lambda will be at the top of the downpipe, probabley just after the turbo, and the heat sensor at the bottom, after the cat.
Looks like this is the one you need (same as the one in the yahoo link?)
Single wire universal M18 thread?