I'm pretty sure you can't get an official LEGO Momoaquaman minifigure (yet), but thanks to the magic of the great big 'F-U' China gives to American copyright laws, you can get a BootLEGO Momoaquaman!
The Batman v Superman version of Aquaman sure has some luxurious locks, and while they don't have the blonde streaks/tips that Aquaman sports in the movie, his arms do sport those sweet Polynesian tattoos!
Momoaquaman is one of the higher-end BootLEGOs. He's pretty high quality - just a smidge south of LEGO quality.
If you're an Aquaman fan and have like .87 cents to spare, you ought to track him down on eBay today!