The correlative ᴹQ. {hríro, hrimiro >>} hrímaro appeared in Demonstrative, Relative, and Correlative Stems (DRC) from 1948 (PE23/112), a combination of ᴹQ. hrim- “many” and ᴹQ. -ro “reasons”.
Neo-Quenya: For purposes of Neo-Quenya I would adapt this to ᴺQ. rímaro “for many reasons” using rim- “many” to be more compatible with Tolkien’s later writings.
The correlative ᴹQ. ondaro appeared in Demonstrative, Relative, and Correlative Stems (DRC) from 1948 (PE23/112), a combination of ᴹQ. on- “same” and ᴹQ. -ro “reason”.
Neo-Quenya: For purposes of Neo-Quenya I would update this to ᴺQ. imaro “for the very same reason” using im- “same”.