Hi I am also from Bangladesh and living in Dhaka too.
I am 30-ish and have been having problem with hair loss. I have been doing extensive research online to help me with my hair loss problem and have a decent understanding and knowledge of the big three, and their availability in Bangladesh (BD).
Currently I am only using generic Minoxdil (also known as Rogaine) and Ketoconazole (also known as Nizoral Shampoo.).
The good news is all three options are available in Bangladesh, are very very cheap and they are made from reputable companies. You might know that Bangladesh has several Pharmaceutical manufacturing companies that exports medicine to about 50+ countries and certified by european, north american and Australian manufacturing standard which makes me confident about buying and using their product. But this is not true for all the pharma, probably the top 4-5 are very good.
I don't know if I can provide link to their product page but I will just write the name of the ones I use:
I use Splendora Minoxidil 5% by Square Pharma. ( you might wanna get a separate "dropper" to apply, I didn't have much luck with their "dropper solution") About 600TK which is about $7.7 for one month's use (60ml).
Dancel Ketoconazole 2% from Incepta pharma. About 140 taka or $2 (60ml).
and if you want to get finasteride (which I don't use yet), there is one called Recur from Beximco and it comes in 1mg and costs about 120 taka or less than $2 for 30 tabs.
All three are reputable companies with good track record, I just started using Minoxidil and keto since the 1st of this month and I am using them religiously but its too early to say anything. Hope this helps you.