A few possibilities:
Edit - actually if you're prepared to do (2), you might as well do (3), as both involve the use of the 9.2 CIAs and sysupdater, but (3) doesn't require you to find a game with <=10.3.
- Check 3dsdb.com and find a game in your region which contains precisely that firmware update. Get a copy of the game, run it, and allow it to update sysnand to 9.2
- Check 3dsdb.com and find a game in your region which contains any firmware version between 9.2 and 10.3. Get a copy of the game, run it, allow it to update sysnand and then use safesysupdater to downgrade to 9.2
- Download the 9.2 update CIAs and use sysupdater to install them
Edit - actually if you're prepared to do (2), you might as well do (3), as both involve the use of the 9.2 CIAs and sysupdater, but (3) doesn't require you to find a game with <=10.3.