This can be written into a file and invoked by

event AS_BINDING l.(load "/path/to/cyrillic.lisp")

from config if you use Lisp-EM.

(defvar *cyrillic-syms* '(
  ("Cyrillic_a" "а" "а")
  ("Cyrillic_be" "б" "б")
  ("Cyrillic_ve" "в" "в")
  ("Cyrillic_ghe" "г" "г")
  ("Cyrillic_de" "д" "д")
  ("Cyrillic_ie" "е" "е")
  ("Cyrillic_io" "ё" "ё")
  ("Cyrillic_zhe" "ж" "ж")
  ("Cyrillic_ze" "з" "з")
  ("Cyrillic_i" "и" "и")
  ("Cyrillic_shorti" "й" "й")
  ("Cyrillic_ka" "к" "к")
  ("Cyrillic_el" "л" "л")
  ("Cyrillic_em" "м" "м")
  ("Cyrillic_en" "н" "н")
  ("Cyrillic_o" "о" "о")
  ("Cyrillic_pe" "п" "п")
  ("Cyrillic_er" "р" "р")
  ("Cyrillic_es" "с" "с")
  ("Cyrillic_te" "т" "т")
  ("Cyrillic_u" "у" "у")
  ("Cyrillic_ef" "ф" "ф")
  ("Cyrillic_ha" "х" "х")
  ("Cyrillic_tse" "ц" "ц")
  ("Cyrillic_che" "ч" "ч")
  ("Cyrillic_sha" "ш" "ш")
  ("Cyrillic_shcha" "щ" "щ")
  ("Cyrillic_hardsign" "ъ" "ъ")
  ("Cyrillic_yeru" "ы" "ы")
  ("Cyrillic_softsign" "ь" "ь")
  ("Cyrillic_e" "э" "э")
  ("Cyrillic_yu" "ю" "ю")
  ("Cyrillic_ya" "я" "я")
  ("Cyrillic_A" "А" "А")
  ("Cyrillic_BE" "Б" "Б")
  ("Cyrillic_VE" "В" "В")
  ("Cyrillic_GHE" "Г" "Г")
  ("Cyrillic_DE" "Д" "Д")
  ("Cyrillic_IE" "Е" "Е")
  ("Cyrillic_IO" "Ё" "Ё")
  ("Cyrillic_ZHE" "Ж" "Ж")
  ("Cyrillic_ZE" "З" "З")
  ("Cyrillic_I" "И" "И")
  ("Cyrillic_SHORTI" "Й" "Й")
  ("Cyrillic_KA" "К" "К")
  ("Cyrillic_EL" "Л" "Л")
  ("Cyrillic_EM" "М" "М")
  ("Cyrillic_EN" "Н" "Н")
  ("Cyrillic_O" "О" "О")
  ("Cyrillic_PE" "П" "П")
  ("Cyrillic_ER" "Р" "Р")
  ("Cyrillic_ES" "С" "С")
  ("Cyrillic_TE" "Т" "Т")
  ("Cyrillic_U" "У" "У")
  ("Cyrillic_EF" "Ф" "Ф")
  ("Cyrillic_HA" "Х" "Х")
  ("Cyrillic_TSE" "Ц" "Ц")
  ("Cyrillic_CHE" "Ч" "Ч")
  ("Cyrillic_SHA" "Ш" "Ш")
  ("Cyrillic_SHCHA" "Щ" "Щ")
  ("Cyrillic_HARDSIGN" "Ъ" "Ъ")
  ("Cyrillic_YERU" "Ы" "Ы")
  ("Cyrillic_SOFTSIGN" "Ь" "Ь")
  ("Cyrillic_E" "Э" "Э")
  ("Cyrillic_YU" "Ю" "Ю")
  ("Cyrillic_YA" "Я" "Я")
  ))

(setf *key-syms* (union *key-syms* *cyrillic-syms* :test 'equal))