GBA:Buttons and Membranes
The buttons in a Game Boy, and the silicone membranes underneath them, usually don't need to be replaced as they can be cleaned upon removal. However there are multiple high quality replacements available in various colors if a different look is desired.
Game Boy Advance (AGB)
Buttons:
BoxyPixel (BoxyPixel machined aluminum face buttons)
BoxyPixel (BoxyPixel machined aluminum L+R triggers, only fits BoxyPixel shell)
ExtremeRate (ExtremeRate buttons, includes plastic Start/Select buttons)
HandHeldLegend (FunnyPlaying buttons)
HandHeldLegend (RetroSix buttons)
HandHeldLegend (RetroSix brass buttons)
HandHeldLegend (ExtremeRate chrome buttons)
RetroGameRepairShop (unbranded clear buttons)
RetroGameRepairShop (unbranded Opaque buttons)
RetroGameRepairShop (FunnyPlaying buttons)
RetroGameRepairShop (RetroCNC machined aluminum buttons)
RetroGameRepairShop (RetroCNC machined aluminum concave buttons)
RetroGameRepairShop (RetroCNC machined copper buttons)
RetroGameRepairShop (unbranded buttons)
RetroModding (unbranded buttons)
RetroModding (Yesterday's Tech Pocket Rock buttons)
RetroModding (FunnyPlaying buttons)
RetroModding (Lab Fifteen buttons)
Membranes:
HandHeldLegend (FunnyPlaying membranes)
HandHeldLegend (RetroSix membranes)
HandHeldLegend (unbranded membranes)
RetroGameRepairShop (unbranded membranes)
RetroGameRepairShop (unbranded membranes)
RetroGameRepairShop (FunnyPlaying membranes)
RetroModding (RetroModding Start/Select membranes)
RetroModding (FunnyPlaying membranes)
Game Boy Advance SP (AGS 001/101)
Buttons:
ExtremeRate (ExtremeRate buttons)
HandHeldLegend (unbranded buttons)
HandHeldLegend (RetroSix buttons)
RetroGameRepairShop (unbranded buttons)
RetroGameRepairShop (unbranded buttons)
RetroGameRepairShop (unbranded clear buttons)
RetroGameRepairShop (RetroCNC machined aluminum buttons)
RetroModding (unbranded buttons)
Membranes:
HandHeldLegend (unbranded membranes)
RetroModding (unbranded membranes)
Game Boy Micro
Buttons:
RetroModding (Lab Fifteen buttons, A+B only)