I agree with the above. Don't give up, just purchase angelfish from people on here or from dedicated websites - paying the shipping costs will be well worth it. Angels Plus seems like a winner if you can't find someone on here with the strains you want...but that seems unlikely.
I wonder if the stores near you have trouble keeping their stock alive also. My LFS (before it closed down
) used to have a nice selection of koi angels, they always looked healthy and I never saw any dead ones, even though they were packed (20 quarter sized angels in a 10 gallon tank). I know for sure they got those locally, I ended up buying equipment from the breeder once he retired. They looked more lively and vibrant than the yellow, marble and platinum angels in the tank next to them, which I am pretty sure were imported.
I really don't think you're doing anything wrong, it seems very unlikely to be an acclimation issue either. It would be nice to get an honest opinion from others in your area, if you belonged to an aquarium club it would be one of those things everyone could gripe about together! The stores probably won't shed any light, although I bet anyone who's been in the business a while can attest to the declining quality of many of the old standbys (tiger barbs, guppies, etc.)
I wonder if the stores near you have trouble keeping their stock alive also. My LFS (before it closed down

I really don't think you're doing anything wrong, it seems very unlikely to be an acclimation issue either. It would be nice to get an honest opinion from others in your area, if you belonged to an aquarium club it would be one of those things everyone could gripe about together! The stores probably won't shed any light, although I bet anyone who's been in the business a while can attest to the declining quality of many of the old standbys (tiger barbs, guppies, etc.)