gguielt_CURRSPRITE element type (added with ggui_element_sprite_current script) is the icon sprite of the currently hovered item in the menu, this is what you want to use here.
Since the data is filled into the menu using ggui_menu_add_option_text it fills the sprite data with NONE, but you could copy ggui_menu_add_option_text and create a new script ggui_menu_add_option_text_and_sprite that also fills the sprite/image data (the two arguments to ggui_fill_meta that are set to NONE within ggui_menu_add_option_text) using two new arguments at the end, and then use that instead in mev_battle_attack. (There's already the _icontext and _gridimage helper scripts that fills the sprite data, but they also set up the elements so that the image is used directly there in the body of the menu, which isn't what you want for this - we want this new script that fills the icon data but doesn't use it yet)