Many Toys For Kids Are Great to Mod & Use With Arduino, Raspberry Pi or others. Here is Robot Arm & Gripper Buying Guide For DIY Electronics.
Duc Thang Nguyen has spent his retirement rendering new machine gears in design software.
[Chiprobot] has created an amazing compliant gripper. Designing robot hands (or end effectors) can be a perilous task. It is easy to give robots big, good, strong hands.