b3b.org
Palindromes are remembered without effort. That is a small cognitive advantage and it applies every time someone tries to recall an address after seeing it once on a conference slide.
B3B reads identically in both directions and sits visually balanced in a logo, which is harder to achieve deliberately than it sounds.
The resemblance to B2B is useful at one remove. An organisation serving business gets the association without adopting an acronym so generic that thousands of entities already share it.
On this extension the string reads as an institution rather than a product. Three characters plus .org is the shape established bodies converge on, and the conventional combinations were gone long before most of those bodies formed.
Symmetrical, short, and permanently scarce.
Offers welcome.