William Kinderman proposes that Beethoven completes the autograph of the Benedictus movement of the Missa Solemnis, op.123, by November 1820. Beethoven moves on October 26th and probably does little work around that time. He therefore has surely begun writing out the autograph for that movement by now; it may already be well along. Beethoven would be doing this work in the mornings, and composing the piano bagatelles for Starke (which will end up as op.119, nrs. 7-11), as well as sketching the Sanctus for the Mass in the afternoons.
Sviatoslav Richter performs the op.119/9 bagatelle in A minor, live in Moscow, 1960 here: