I would not try to protect the cover only. The extra weight and "pull" of the protective sleeve might cause the front cover to detach more easily.
I would just order one of these, and slide out the entire Magazine on the rare occasion you flip the pages/read it...
https://www.ebay.com/itm/36355490491...8AAOSw4DJYgSyc
https://www.ebay.com/itm/20376740323...kAAOSw8eZhyjBA
These Magazine Toploaders are rigid enough that you can easily display the Magazine on an easel or tripod as a backdrop for your cards.