* For what purpose, e.g. performance? (If so, on what instrument? And yes, I know 2 staves implies keyboard, but it has to be asked.) For the equivalent of classroom learning?
* What repertoire? (If the classic repertoire, then files are more easily obtained in a variety of electronic formats – and there are many possible sources. If nothing more sophisticated than MIDI is available, then it is relatively straightforward to translate and correct to a Sibelius or MusicXML equivalent. Copyrighted materials on the other hand usually require talking to the publisher to allow customised arrangements.)
* When you say larger ensemble pieces: do keyboard reductions already exist of the repertoire, or would extra effort be required for these to be transcribed? (Again, depending on the repertoire the availability of notation files or just a MIDI file could speed the translation process.)
To list a few websites that have some of these resources: ClassicalArchives.com (MIDI files); SibeliusMusic.com; FinaleMusic.com/showcase; MidiWorld.org; etc...
These queries come up from time to time, and the reason they are not necessarily always well addressed at IMSLP is because the sight-impaired musical community is a relatively small proportion of the whole, and so requests for Braille material are often addressed case-by-case rather than at a fundamental basis of availability of performance and teaching scores/parts; also, the vast majority of contributions here are scans of already printed material – not new editions with the associated typesetting notation formats, which involve their own issues.