Your choice to purchase a sovereign gold bond is laudable.
Unfortunately, you will not be able to buy an SGB in time for Dhanteras or Diwali. This is because the government releases SGBs for subscription every few days. For October the subscription date was till October 19, with issuance on October 23.
However, you can still invest in a sovereign gold bond in November as the next tranche of sovereign gold bond will begin from November 5-9 with issuance on November 13.
Thus, you can time your sovereign gold bond (SGB) purchase with Dhanteras and purchase gold in a hassle free and safe manner.