Getting decent inline switches is a major PITA. sure, Jaycar sell stuff, but the moment they get any moisture(rain, drip, condensation, rainy packup), they turn to crap and it will be the same with any flea-bay offering as they all come from China.
One of my routine maintenance activities is replacing non-working switches in 12V switch boxes that I built with gear from Jaycar/China. you get what you pay for.
If you can not find it in the online catalogue, then they probably don't have it.
Search for "inline switch" CAT. NO. SK0998 is probably usable, but at $8 each ouch and you really do not want the plug and socket.
At one stage(decade ago?) they sold a 240 lamp light inline switch for twin/figure 8 cord, which would have been good for you need. I haven't seen them around for about the same time(legislation changes).
If you have a source of film canisters/test strip containers/plastic pill bottles or similar, then have a look at these;
http://www.jaycar.com.au/productView.asp?ID=SK0960
10mm mounting hole in the bottom of the above, feed the wires through, solder or crimp to slides and you're away. Only 10 for $20.
I'd get a push button version for taking volt meter readings.