What are the Chinese characters for the names of the Chinese American characters?
From circumstantial evidence, I would guess that we do not have any systematic information about character names, insofar as there are a number of inconsistencies and as the listings on the Chinese language Wikipedia page for Banana Fish seem somewhat implausible.

In the section of the manga that follows Yut-Lung's introduction, we see him address Shorter in Chinese. Shorter's name is written as 肖达. This appears to be a Mandarin transcription (xiào dá) of Shorter's name. In fact, the Cantonese pronunciation of the characters 肖 and 达 (達 in the traditional form) do not produce a plausible transcription for Shorter, and a better transcription for the first syllable can probably be found.
Shorter's surname is Wong, which is typically derived from the Cantonese reading of 王 or 黃. (Wikipedia also lists 汪, which is significantly less common.) However, the Chinese Wikipedia lists Shorter's surname as 翁, which does not appear to be read as Wong in any Chinese dialect. Japanese Wikipedia only gives the katakana for Shorter Wong.

Sing's name is listed as 辛舒霖 on Chinese Wikipedia, 辛 being his surname, but his entry on Japanese Wikipedia only contains katakana. In a conversation with Yut-Long later in the manga, it is revealed that his name means &quot;devil.&quot; But 舒 means comfortable and 霖 refers to rain. Moreover, 灵 is a much more obvious character choice for the syllable ling, as it means spirit.

Lee Wang-Lung is a mish-mash of Cantonese (Lee Wong-Lung) and Mandarin (Li Wanglong) pronunciation of the constituent characters. There is a similar problem with Lee Hua-Lung (Lee Wah-Lung and Li Hualong)