There are a lot of different versions of the Big Bass Bonanza game, so this is a slightly tricky question to answer. And it is also something that is generally time bound. What we mean by that is that most promo offers, beyond the welcome bonus, are for a limited time.
So, while it is possible that there are Big Bass Bonanza bonuses available right now, it is difficult to tell you exactly where. Your best bet would be to do a bit of a deeper search to see if there are any Big Bass Bonanza free spin bonuses on the table at any given online casino you are interested in – as a free spins promo is the type of applicable bonus you would find.
Another option, needless to say, is to use your welcome bonus cash to play. And since most online casinos slots play counts 100% towards your bonus playthrough, this would actually make for a particular win-win kind of choice.