Replacement Glass lenses for the WonderSwan. Often, IPS screen kits come with one, though they might not always be a match for your specific WonderSwan Color version.
WonderSwan
Where to buy:
No retro shops seem to have this in stock, but you can sometimes find it on AliExpress.
WonderSwan Color
Where to buy:
Retro Game Repair Shop - Replacement lens (Including versions for limited edition models).
WonderSwan Crystal
Where to buy:
Retro Game Repair Shop - Replacement glass lens.