Hi, I don't know if I'm too late.
In singapore, there are 2 malls famous for their IT products, Funan and Sim Lim.
I bought my leather case for my Polaris at Funan (level 2) for $25, and I think there are cheaper ones. Ground level has a few push cart stalls that sell the same thing too.
Sim Lim ground level has quite a lot of stalls that sell casings for all types of mobiles. Either the 5th or 6th level there is a shop called Million Mobile (or something to that effect) that has tons of mobile accessories, including Polaris cases.