Here are 2 schedules that you could use. I believe consecutive byes have been reduced as much as possible.
13 players A to M on 4 courts for 20 rounds
(C I) (G L) (---) (---)
(D F) (J K) (A H) (B E)
(C E) (G H) (I L) (K M)
(B M) (A D) (E J) (F I)
(J L) (F K) (C H) (A G)
(A B) (G M) (D H) (E I)
(B L) (F J) (I K) (C M)
(C G) (E H) (A M) (B D)
(D J) (K L) (B I) (C F)
(H K) (A E) (D M) (G J)
(G I) (C D) (B F) (E L)
(H M) (I J) (A K) (C L)
(D E) (B G) (F L) (A I)
(H J) (A C) (E M) (B K)
(F M) (D I) (E G) (H L)
(G K) (B C) (D L) (A J)
(H I) (E F) (C K) (J M)
(A L) (B H) (F G) (D K)
(E K) (I M) (C J) (F H)
(A F) (L M) (B J) (D G)
14 players A to N of 4 courts for 23 rounds
(D M) (F G) (H K) (---)
(A N) (B J) (I L) (C E)
(B H) (K M) (F N) (D G)
(C I) (D L) (E J) (A F)
(B L) (E K) (G N) (H M)
(E I) (A C) (D F) (H J)
(B N) (G I) (A M) (K L)
(D H) (C G) (B E) (F J)
(A K) (H L) (I J) (M N)
(E F) (I N) (C D) (B G)
(A H) (J N) (L M) (I K)
(C F) (A D) (E G) (B M)
(D K) (J L) (H N) (B I)
(C J) (A E) (F L) (G M)
(B F) (H I) (J K) (D N)
(G L) (C M) (A I) (E H)
(G J) (B D) (C N) (F K)
(F I) (C H) (E M) (A L)
(A G) (B K) (D J) (E N)
(I M) (F H) (G K) (C L)
(K N) (D E) (B C) (A J)
(E L) (F M) (G H) (D I)
(J M) (L N) (A B) (C K)
