In Japan, the list prices for US-made shoes are astronomical. Unless you happen to be able to find some old stock sold at 30% discount or more, I don't think it is worth the while. I've yet to find them in the shops for below 25,000yen or around SGD370, but maybe I haven't looked hard enough. The question is, you just want to save around $50 and expect your sis, who is on holiday, to waste her time going around searching for them and then having to add to her luggage burden (in both volume and weight) if there really is the model and size you want?
May be alittle cheaper in Hong Kong but I rarely see them.
Are you familiar with their sizing? If not, you should try them out locally before you buy. AFAIK, Suntec is fixed pricing but service is not bad. Peninsula, I think Feder sports sells them, with a little lee-way for bargaining but like most places, models and sizes very limited.
If you are familiar with your sizing, and assuming the company doesn't send you a damaged pair, online is still cheapest and most convenient.