There's a whole industry catering to that niche. Magazines like Luxury Launches [1] or Robb Report [2] and retailers like James Edition [3]. You can tell them apart from normal retailers because the menu will have categories for jewelry and helicopters.
For example, here's a $990 100mL bottle of Balsamic vinegar I found on Robb Report that's aged for a century [4].
Most of these are for private concierges and assistants, though, as very rich people don't usually bother with this stuff themselves. They get their staff to source it online or find someone to hand craft a custom piece to spec. "Personal shopper" is the generic term
For example, here's a $990 100mL bottle of Balsamic vinegar I found on Robb Report that's aged for a century [4].
Most of these are for private concierges and assistants, though, as very rich people don't usually bother with this stuff themselves. They get their staff to source it online or find someone to hand craft a custom piece to spec. "Personal shopper" is the generic term
[1] https://luxurylaunches.com/
[2] https://robbreport.com/
[3] https://www.jamesedition.com/
[4] https://giusti.it/en/prodotto/giusti-100-100ml/