This isn't precisely what you asked for but yet it's not specifically just a "supply" problem, but in my opinion (or should I say... for my needs
) where the biggest hole comes is in the availability of bulk handgun bullets.
Obviously, 9mm and .45 are amongst the leaders in handgunning popularity and there are multiple bulk sources for jacketed bullets for these guys. And plated works awfully well for those who need some of the jacketed qualities that you don't get from cast lead bullets, and you can buy plated bullets in bulk. But there's a place where plated bullets have their limit and only jacketed will do and yet there are either none or extremely limited venues for bulk
bullets. I'm talking about making purchases no smaller than 1,000 pieces and more commonly at around 3,000 pieces & beyond.
--The most glaringly obvious one is a .357" true jacketed slug available in bulk. Zero and Montana Gold may be the only bulk suppliers. Hard to count Nosler's 250-pack as bulk given that it's only 250...and expensive.
--For a select few of us on Earth...a bulk jacketed .312" handgun bullet (85-115 gr w/cannelure) sure would be nice. Nobody in the world makes such a beast.
--Bulk jacketed in .41" and .429" would sure come in handy.
No doubt, Hornady makes some terrific bullets in -ANY- of the sizes I just pointed out. Extremely high quality and accurate. But if you simply want volume for the pure enjoyment of a lot of trigger time with all
of your handguns, you'd go half broke buying these slugs at retail, 100 pieces at a time.
So while the "industry demand" isn't all too great for the things I pointed out... I believe that if someone offered
them, someone would sell a holy hella lot of them.