I would try the above the 3 sites posted above your post. But most of the links I try does not work. gimy.ai seems to have one or two working streaming videos working for me.

Side note, as the show is over 20+ years old. There is no way for any download link to still work.

Next best option is to search for it on youtube. Sometimes youtube is excellent for these super old shows since copyright claims are probably over. Just to list a few that I found:

古惑仔1之人在江湖
古惑仔3：之只手遮天
古惑仔Ⅲ之隻手遮天
古惑仔之九龙冰室