Found the deal on Amazon for LEGO® Super Mario™ Bowser's Castle Boss Battle Expansion Set 71369 Building Kit for 108$, cheaper than even on BIG W (with 20% off).
same price at catch
Catch is sold by Target so would have same price as Target
Price matching the current Target Sale
Thanks OP. Son's birthday present sorted! :)
Note: the Bowser Castle is an expansion set, so you'll need to Base Mario Starter Course for the full potential.
Thanks! Yep got it already :)