When my kid was going for her prosthetics the prosthetist said most finger prosthetics are for aesthetic purposes. Depending on your specific needs there might be options for you, and DIYers have made some impressive prototypes, but they all have their pros and cons. I think the Hero Hand is a pretty impressive option, but it is really expensive and some folks might have trouble getting insurance to cover it. Plus for kids the more expensive and complicated prosthetics aren’t great options as they tend to break them and lose parts. I was told that most folks with a partial hand, due to birth defect or amputation, choose to just work around it rather than wear a prosthetic.