Blacklight bulbs
20W T12 FLUORESCENT BLACKLIGHT MEDIUM BIPIN BASE -- topbulb.com
found on t-shirtforums.com

Ballast and Fluorescent Tubes FAQs -- GE

LITHONIA Fixture, Industrial, F20T12, 20 W, 120 V
Channel Width 4-3/8"
$68.40

Lumapro 2UWU1 Channel Strip Fluorescent Fixture F20T12
4-5/8 Width
$33