Dear Respected Forum Members,
As Salaam U Alaikum Wa Rahmatullah.
Concerning the above issue, I would like to inform that, there are some places where, winter clothes are available throughout the year. One of those places is "Rumi Shumi Garments", Bongo Bazaar, Dhaka. You should visit Bongo bazaar and explore yourself. You may find more places like this.
You may also explore ARTISAN, Uttara and MOSTOFA MART, Bashundhara City for Quality Winter Clothes. Still some are there.
BTW, please take only necessary clothes, a pair of running shoes (Lotto may be a good choice, Italian brand, comparatively cheap, quality product)
Best regards,
INDIANAJONES.