Just thought i would throw this out if anyone is interested. Not lowering springs, per say, but I found a set of height adjustable coilovers that would be likely to work on the Scion iA. Tein USA allows to special order their "Street Basis" Coilovers (Part Num: GSMC2-11AS2) for $750 that were made for the latest gen Demio (aka Mazda2). Note that the DJ chassis Demio(which is the model Mazda2 that our iA is based off) started in Japan in Oct 2014 model year.
Go here:
http://www.tein.com/srch/us_search.php
Choose Mazda ---> Demio ---> 2014.10 and the part (above) should pop up.
Now it specifically mentions the DJ5FS Chassis, which I think is referring to the Hatchback (not Sedan), however I SERIOUSLY doubt that there is much difference in the suspension between the two, and appears to be less than 100lbs difference in weight. Also note, these coilovers are more for comfort than performance, according to their blurb: "THE SETTING IS MAINLY FOCUSED ON REMEDYING THE ORIGINAL CAR'S STIFF RIDE WHEN GOING OVER GAPS AT LOW SPEED. STABILITY AND RIDE COMFORT ARE WELL BALANCED, WITH MILDER-THAN-ORIGINAL SETTING FOR LOW-SPEED DRIVING ON STREETS AND WITH ADEQUATE SUPPRESSING FEEL FOR MID-TO-HIGH-SPEED DRIVING."
Just thought id share. Hopefully more iA (or at least sedan) specific options soon.