I'm still searching for that. The closest I've come to finding a tape solution is black masking tape:
The thinner the better. I've used 1/4" black tape (could be the same brand above) on bellows. Getting the inside grooves of the bellows is easy. But the outside corners is hard to get with tape. And I don't have the steadiest hands.
Someone's mentioned to use gaffers tape in the past. But isn't gaffers tape a little thick?