I think a light/laser combo would be feasible for a J-frame... so long as people appropriately adjusted their expectations of the light.
When we're talking about carbines, duty handguns, or other "primary" weapons, I can understand the desire for MOAR LUMENS!!!! But the J-frame occupies a different role.
The above linked griplight is 100+ lumens. That's "dim" by today's standards, but it wasn't very long ago that 60 lumens was considered a "tactical" light suitable for duty use (original Surefire 6P, for example).
I remember having a conversation with Craig (SouthNarc) back in 2008. He had approached Crimson Trace about making a set of their laser grips where the laser emitter was replaced by a small LED (no reflector or anything special: just a single LED that would put out a small flood pattern of light)*. The idea wasn't to put out a huge amount of light, but just to give the user
some light, at the very least allowing for better target identification and/or some navigation in dark spaces. From what he said, Crimson Trace had no interest at all.
*Something like the thousands of
5mm keychain LEDs on the market
If Crimson Trace (or whoever) paired a laser with a low-powered LED like above, I think they could have a winner. I also think it could be done with minimal addition of bulk (certainly less than the Hyskore's Griplight). Those LEDs, after all, can run off of 2016 or 2032 cells (the latter of which is already used by laser grips).
Again, it would not be a lot of light, but it would be
something, and I really do believe it could be done with minimal addition of bulk (just enough extra housing for the 5mm led to sit somewhere near the laser emitter). It wouldn't be able to blind anyone, and the light would easily wash out under external sources (like a street light), but in darker conditions could be quite useful.