I think your goal for having braille on museum materials and information documents is truly a great leading endeavor. Not every blind person can hear audio exhibits or when in a group it can be noisy as well. Using an audio app for blind persons might be a good idea too. Advocating the inclusion of people with disabilities is not only very honorable, but highlights a museum's mission in serving the public. 

What organizations have you approached? I believe there are a couple of org.'s that might be of help: AFB - American Foundation for the Blind is one that may be of some help in finding a company to produce your materials, or the Kansas Braille Transcription Institute mentioned by Katie Keckeisen.