Where does the Asian dish "sang choi bow" come from?
Probably Hong Kong.

It is written in Chinese as "生菜包", which in Pinyin is "shēngcài bāo", noticeably different to any of its usual spellings in English.
However, in Cantonese it is "sang1 choi3 baau1". Much closer to the English spellings and pronunciation. Cantonese is mainly spoken in Hong Kong, a great culinary exporter and major influence on "Chinese food" in the west.

生菜 means "lettuce" and 包 means "wrap", etc.

It does in fact have a Wikipedia article, but only on the Chinese Wikipedia. The article is very short and Google Translate does not handle it well. I will include the Chinese text here in case any readers who can read Chinese can find something of the dish's origin or history:


  生菜包
  维基百科，自由的百科全书
  
  生菜包是一种食品，寓意“生财”。
  
  起源
  
  生菜包源自广州市芳村的坑口生菜会，该活动举办的时间为从农历廿四至廿九一连六日（旧称前三日后三日），这里会设有戏台和比武台，唱粤曲的，舞狮的和比武的登台。为供村民观赏之余家人朋友共聚用餐，小贩便推出生菜包。
  
  材料
  
  生菜菜叶包着特制的饭菜（通常有蚬肉碱菜等馅料）。
  
  這是與食物相關的小作品。你可以通过编辑或修订扩充其内容。


Of course it's still possible the dish originated outside Hong Kong, the name is very literal and isn't necessarily the original name of the dish. But it is clear it came to the English speaking world by way of Hong Kong.