My favorite bits are PBSwiss. They have sets available or can get individual bits and build your own custom set with just what you want/need.
https://pbtools.us/1-4-screwdriver-power-bits_c17.htm
Skid Factory - They have several builds on the Mighty Car Mods guys second channel; Really well done. Burned several evenings staying up too late to watch "one more episode"
This Old Tony - I have over 200 youtube channel subscriptions, This Old Tony is the only channel that I have the...
Is the design intent to have less weight/force spread over a larger impact surface area? What kind of jobs would a hammer like this be useful for vs. one of the other Trusty-Cook deadblow hammers?
You might also want to spend some time lurking over at the Practical Machinist forums as well if you've not found them yet. They have machine specific subforums with many old tool rebuild threads so you can see what others have bought and what they went through to get them functional again...