I had a similar problem, I emailed all rescues within a 50 mile radius asking whether they would consider homing two indoor kittens. I explained my home set up, why they would need to be indoor, how long I worked, the fact that I have cat proofed windows, how I appreciated indoor cats required more attention and stimulation, how I'd be prepared to home kittens with speiail needs, how if I was out of their catchment area I could provide vet references and/or donate to another charity to do a homecheck on their behalf etc etc. The majority of replies were a blanket No and some implied it was wrong to even consider homing kittens indoors. CP said No, RSPCA said Yes. I think about 4 out of 20 said Yes...
I eventually found my gorgeous baby boys and I know they will have the best life possible with me with lots of love, stimulation and attention. If I move in the future to somewhere with a garden suitable for cat proofing then I will do that as I think that's the ideal solution in any case, it's a cruel world out there and I don't want to expose my boys to it.