There are more words but they are from Tolkien's earlier conceptional periods. Tolkien likely changed these words as he evolved the aesthetics and completeness of the languages. You may even find languages that Tolkien later rejected. Do not mix words from different time periods unless you are familiar with the phonetic developments.
qapa-
verb. to chaffer, bargain, swap, barter
qap-
verb. to throb, flutter
A verb appearing in the Early Qenya Phonology of the 1920s with glosses “throb, flutter”, derived from ᴱ✶ku̯ap- as an elaboration of ᴱ√kapa “leap” (PE14/66). Oddly, Tolkien gave it the primitive form ᴱ✶skapi̯a-. The verb qap- might be a later iteration of ᴱQ. papa- “tremble” from the Qenya Lexicon of the 1910s (QL/72). Compare also the possibly related verb ᴱN. gobab- “shake” (PE13/132).
Below: Tolkien's Late Period (1950–1973). These are from Tolkien's late conceptual period — his most settled forms of the languages. Prefer these over the earlier ones above when composing new text.
A verb appearing as ᴱQ. qapa- “chaffer, bargain, swap, barter” in the Qenya Lexicon under the early root ᴱ√QAPA “chaffer” [= haggle] (QL/76).
Neo-Quenya: I would retain ᴺQ. quap- “chaffer, bargain, swap, barter” for purposes of Neo-Quenya derived from a Neo-Root ᴺS. √KWAP, since we otherwise have very few words having to do with commerce.