I have seen Tourna butt caps with no branding - but I've not used one. I thought they had them here at TW but it appears not. Google "Tourna Butt Cap" or "Generic Butt Cap Standard" and look down a few links. One place has them for $1.67 each.
Prince Tour Diablo Mid - Iontec Black 1.20 @ 45 - Wilson Pro Overgrip