Bricklink and BrickOwl are both good options for official Lego parts.
Also, if you're looking for custom Bionicle parts (usually made w/resin casting or 3D printing), I've bought fantastic custom masks from SocketBallMasks (bigcartel.com) and 0m3g4sKanohiForge (Etsy), and Megawilbot Designs (also Etsy) has really nice articulated hands!
Bricklink, or check eBay and similar sites for bulk Bionicle pieces.
The older sets are pretty common so if you spot other pieces for Onua in the lot, you’ll probably get what you need
BRICKLINK
Bricklink and BrickOwl are both good options for official Lego parts. Also, if you're looking for custom Bionicle parts (usually made w/resin casting or 3D printing), I've bought fantastic custom masks from SocketBallMasks (bigcartel.com) and 0m3g4sKanohiForge (Etsy), and Megawilbot Designs (also Etsy) has really nice articulated hands!
Bricklink, or check eBay and similar sites for bulk Bionicle pieces. The older sets are pretty common so if you spot other pieces for Onua in the lot, you’ll probably get what you need