Here's a few places for you that stock/have stocked B+W:

Wing Shing in Mongkok:
Sun Sam in TST;
Shing Shing;
Tung Ting in TST; and
DC Fever in Mongkok.

Apart from Wing Shing the other stores I never go to but do know that they stock B+W filters.

Just ensure that the filter you get is MRC coated. Even Man Shing sometimes doesn't have availability of the B+W MRC filters. The non MRC filters are next to useless.

And welcome to the world of tripod purchases . It's an absolute nightmare and expensive - look to be spending a small fortune for anything that offers reasonable support and security. I shudder to think how much I've spent and how many brain cells I've lost working out the best combo

Buying seperate legs and head is the best solution. Stability, security, ease of set up and portability should be key when it comes to buying a tripod. Unfortunately with the cheap tripod/head combos you lack all of these.

Not sure what you need the tripod for but I've got a near new 4 section carbon fibre tripod that I rarely use that I'm looking to sell. It's got twist locks though and will be selling for around $1,300. It'll work great as a both a table top and full sized tripod given it's folded size. PM me if you want to check it out.