If you already have a camera in your inventory, and you buy a higher model, I believe it upgrades the previous one to that higher model without adding another camera to your inventory. But you can remove the camera you currently have in your inventory by installing the Universal Ren'Py Mod (URM) and then buy another camera to Lia in the shop.
although I'm not sure if by doing it this way, that camera you deleted might reappear in the future after buying some other item to Lia in the shop. Just in case everything you manipulate in this way is saved in new savegames, keeping the old saves as well so you can reload them if necessary.
At the end of this other
post, you have how to manipulate some inventory items with the command console.