In my experience, all three Vegas stores act like “Birkin” and “Kelly” are a foreign language until you become an established customer. I don’t think any of them will take kindly to the suggestion of a pre purchase agreement where “I promise to buy X if you also let me buy a Y B25“ Perhaps if you spent 5x they may say they would be willing to try to source one for you in the future, however, even if they were up for the deal, they likely wouldn’t have a particular spec available immediately regardless. Vegas has tons of long term big spenders, especially from the Southern California region, and relatively few B25s which are immediately offered to favored clientele. There is always the minute chance of a new customer miracle but in general, H is a game of patience, not demands.
I suggested to be mindful of making an appointment if you only intend to buy if a B25 is offered because these are sales people who make their living off commissions. With the current pandemic, their opportunities to make a sale from one of their clients are significantly reduced to just ~6 appointments/day, 5 days/fortnight. It was a suggestion of common curtesy and compassion; they don’t control the bag offers.