The Gnomish Lexicon of the 1910s had G. bageth, first given as the equivalent of G. banc “trade” and then revised to mean “market” (GL/21). It was marked “pl.” indicating it was a plural word, and was clearly based on G. bag- “trade” (GL/21). Early Noldorin Word-lists of the 1920s had ᴱN. bagarth “market”, also based on ᴱN. bag- “trade” (PE13/138).
Neo-Sindarin: For purposes of Neo-Sindarin I would adapt these “market” words as ᴺS. bangath, an abstract noun based on the later verb [N.] banga- “trade”.
A noun appearing as {bangul >> bangol >>} G. bang “staff” in the Gnomish Lexicon of the 1910s (GL/21). The deleted forms were perhaps cognates of ᴱQ. vandl “staff” appearing in the contemporaneous Qenya Lexicon under the early root ᴱ√VAHA having to do with travel (QL/99), but in the Gnomish Lexicon proper Tolkien gave the Qenya cognate as ᴱQ. vanga. As for the Gnomish form, it reappeared as ᴱN. bang “staff” in Early Noldorin Word-lists of the 1920s (PE13/138).
Neo-Sindarin: I’d retain ᴺS. bang “staff” for purposes of Neo-Sindarin.