I used to use a lot of IMR 700X and IMR PB and had difficulty at times finding either powder. Two years ago I switched to Alliant E3 and Alliant Green Dot and have not experienced any supply problems.
I used to use 700X because it was a little more dense (took up less volume) than Alliant Red Dot. This really improved the crimps on my Federal Paper reloads. Alliant E3 is also denser that Red Dot and I get good crimps with E3 in my Federal Paper reloads. I also found that I get the same performance (1 1/8 oz at 1145fps) from 16.5 grains of Alliant E3 as I did with 18 grains of IMR 700X.
You may want to switch to Alliant E3. It costs a little more than IMR 700X but if the additional cost is offset by the improved efficiency of Alliant E3.
As to replacing IMR PB with Alliant Green Dot, both are great handicap powders but I find that I use about 10% less powder when I use Alliant Green Dot over IMR PB. The newer Alliant Green Dot is cleaner than the older version and costs way less, pound for pound, than IMR PB.
I really like Alliant E3 in 1 oz. loads in Remington STS hulls with the Remington TGT12S wad.
Hodgdon, IMR, and Winchester are all the same company. These suppliers have cut back production on 4 and 8 pound containers. They are trying to move all the surplus of 1 pound containers. This is what my powder distributor told me.
My source is having problems getting H-110 or W-296 in 1lb cans, I had to go with the 4lb can of W-296. With the cost of reloading, I am going to practice ALOT with the .410 luckly I have plenty of hulls.