My recommendation for all A's fans is to purchase Giants stuff and drive across the Bay Bridge! That may sound as palatable as drinking Drano, but honestly there is zero chance Oakland ever gets another MLB team.
Perhaps it was before your time, but one thing A's fans can really savor forever is the dynasty team from the 70's that won three World Series in a row (1972-74). There was a small connection for me in that Jim Hunter was from my neck of the woods in North Carolina.
But, Charlie Finley was a noted cheapskate and rather than pay his players their market value, he let them sail off to other teams. Finley's moves to trade away his best players actually invoked a rare use of the "best interest of baseball" power of the MLB Commissioner. Bowie Kuhn voided those ridiculously lop-sided trades, all because Finley wanted to get rid of all his players who would be eligible for larger contracts under the new free agency rule.
That was the start of the downfall for the A's, even as the Bash Brothers team reached two World Series in the 1990's, winning one against the Giants, and losing the other to the underdog Dodgers.