staining - Is there a photobleaching-resistant, cell-permeant viability stain in the far red part of the spectrum?

I am looking for a live-cell–impermeable dye for viability. (The cells cannot be permeabilized and fixed in this experiment.) I would prefer with excitation and emission spectra similar to Cy5, but I can be flexible here as long as the spectra are far away from Hoechst.

I have tried TOPRO3, but it seems to lose its brightness after a few exposures, so I would like something more resistant to photobleaching.