There is search engine called google….
Monsey Hat Box, Cuff and Co and the hat source to name a few. Hats today are super expensive to me at least.
There is another option which my son has tried for a weekday hat. He is a bochur up in Yeshiva of Rochester (NY). There is a Rebbe there that has a side business that has a website yeshivish hats dot com (all one word). There pricing is very reasonable for those that cannot afford or want to spend $200+ on hats. I guess you will need to know your hat size since it’s online, unless you happen to be driving by the area.
I do NOT know about quality or anything else. You can always ask for references I guess. They have a few google reviews and they have testimonials on their website.