Relentlessly phone distributors (e.g. Ingram Micro), followed by large resellers (Ballicom, Lambdatek, Scan, Novatech, Insight etc), followed by smaller resellers (Boston etc), followed by scalping drop-shippers (ECPROF, tekshop247 etc). Ignore what the websites say and talk to actual humans. You'll need to open trade accounts with most resellers to be able to have conversations with account managers who have the authority to actually get stuff done and push for real ETAs.
All of this takes time, you have to be prepared to put the effort in.
I've also had success with HPE 'upgrade' kits from HPE distributors in the recent past.