This is just a quick modification I did to the silver_cage.stl and silver_prong.sttl files to allow for a small 4mm diameter compression spring to make the prongs spring-loaded. I used a cut-up pen spring for this, but a properly sized spring would be even better. Additionally, the spring should not be very powerful, as the prongs will not fully close if the spring is too powerful. Acquire the rest of the files from here: https://www.thingiverse.com/thing:169870
Special thanks to Ellindsey for making such a high-quality model for free. All credit for the base geometry goes to them. All I did was add some 4mm diameter circular divots to their model.