Alterations display control

[Menu Jacques]

Hello folks,

Is there a way to force a flat sign for all ees’s and bes’s in the following 
example, without using ! for each of them?

Choosing a c \major key would do it, but the actual key information would then 
be lost.

Thanks for the help!

JM


\version "2.19.22"

\relative {
  \clef "bass"
  \key bes \major
  %\key c \major
  f16 [ f,16 a16 c16 ] f16 [ c'16 a16 f16 ] g16 [ a16
  bes16 a16 ] g16 [ f16 es16 d16 ] | % 138
  es16 [ f16 es16 d16 ] es16 [ c16 d16 es16 ] f4 f,4 | % 139
}