Probably there are a number of options. I have used BioTek Neo platereader and it works well at least for different multiwell plates and if very high resolution is not needed. Good physicist could probable connect every spectrometer with a plate-reading systems by using light guides, but commercial platereaders with monochromators would be more simple to operate.
As the poster writes about solid samples and single cell holders, he might have a hard time doing this with a plate reader... So, I would tend to recommend a general-purpose fluorescence spectrometer with exchangeable sample holding accessories. Still won't advice any manufacturer without knowing his desired performance and price range...
Solid samples are no real issue for platereaders. Specially if only spectra are required. Quantification is more problematic, but even with spectrometers you probably need an integration sphere to to it properly for solid samples.
Single cell could be an issue, but may be not a major one if the software is flexible. But of course there should be available spectrometers that read multi well plates.