BASS Pro Shop
Last night they had plenty of all shot sizes on the shelf. If you get an Outdoors Rewards Card new then you get $15 off your first purchase. I did not see additional rebates for them there.
They also had Win 3-2 X and 2 3/4-X and 3.5 - 2.25-X so they are well stocked with shells and putting out calls as I left.
Remington is offering $3 off per box up to 4 boxes . Their 3"-1 7/8-4/5/6 (your choice) were like $10.47 per box.
The Bass Pro website also has free shipping (no minimum) if you use freefeb.