I like the Impact ones... can get from Isetan. The smallest sized ones cost a little over 80bucks... but the biggest ones are about 95 or something. Not sure about the SPI ones though.
I bought for my son and he used it in P1 this year... survived his rough handling, and light enough yet spacious enough.
So I bought for my daughter for P1 next year also. Only thing is no design... just plain colours.. and only 3 colours... pink, navy blue and royal/bright blue.
Crosscom can be found at suntec city, near to toys r us. but i found their bags very boxy, and extremely expensive.