Hi there!
Yes I realize there are plenty of third-party mag reloading devices out there... but how many can you use with just one hand? Its not a new ultra secret design - yet you have probably seen them ... on a regular basis for many, many years. My eureka moment is due to the fact I have the use of only one hand... therefore any multi-handed functions are automatically ruled out. The focus was trying to simplify a way to capture and retain the spring tension within the magazine AND using my remaining hand to feed the mag.
Was it expensive? Nope. You probably have a few already lying around.
If not; any office supply store will have them.
Below is my example - using a S&W Victory mag.... using the medium size. If your spring tension is a bit stiff... just use two- stacked one above the other.