203B continues in stock currently at Powder Valley which I think is still the best answer to the OP.
I am reminded of an interesting conversation some years ago on a related subject - definitely NOT RL-15/Norma 203B.
Dealing with two different OEM type vendors with very similar product lines - neither company made everything sold under its own name and actively cross licensed and filled their lines with their competitor's production.
In fact a salesman for company B suggested in some seriousness or at least kidding on the square that we should buy company A's production under the Company B label (where we could) for about the same cost to us.
The rationale was that in this era of statistical process control Company B's deal was for only from the better half of the production so that Company B would not eternally get the inferior half of the production by Company A.
I've long understood going back to Phil Sharpe and others that powder as produced varies and some is sold to consumers as meeting tests for canister grade and some is sold to loading companies as needing and getting adjustments. Mostly first you make the powder then you test it and label it after testing the final product.
I can only interpret statements by Norma that what they sell themselves is the best as their own canister grade is maybe down the middle of the statistical process control or maybe more attention is paid to contaminants or storage condition or something. I doubt the claims are baseless but in a world where leaving the powder exposed to the air for a few day's of lab work changes the result by weight I'd have real trouble designing an experiment to refute the null hypothesis that they are the same. Sadly I'd have real trouble trying to refute the null hypothesis they are different.
I'd expect to punt and say the same but not identical under rigorous testing but that's why the tests. I'll be more interested in the procedure than the result I think.
