In a medium skillet over medium-low heat, cook butter swirling pan often until foaming subsides, about 2 minutes.
Add panko to pan, stirring often, until panko is golden brown, about 3 minutes and season with salt. Remove panko from pan and set aside.
Heat a gas or charcoal grill to medium-high (400°F to 475°F).
Place oysters cup side down on grill. Cover grill and cook until the first oyster opens, about 5 minutes.
Remove oysters from grill with tongs, keeping cup side down. Carefully use an oyster or paring knife to pry the top shell open, discard. Carefully run the paring knife underneath the oyster meat to release it from the shell.
Drop about a tablespoon of the Maikaʻi dip into each oyster and top with toasted panko, carefully return to the grill. Cover grill and cook until the dip is completely melted and slightly bubbling, about 4 minutes.
Transfer the oysters to a wide, shallow plate and serve immediately with lemon wedges.