I have never seen anyone selling cast bullets for the 32 special other than 170s, but I've never really searched for them.
If you are looking for a good powder for both cast and full power jacketed loads, H4895 is probably a good choice. Others will have their favorites. IMR 3031 is very popular and has been for a long time.
If you want a powder specifically for the lighter cast load, you can use a slightly faster powder. H4198 or Reloader 7 come to mind. There are 2 powders that were invented for lighter loads: SR4759 and 5744. They both use lots of case capacity per grain, which is a plus when downloading.
I use Reloader 7 and SR4759 everywhere they fit. There are lots of options and I am sure you will find something that works for you.
Enjoy,
Bob A