Fuorescent paint -> Jarrier Book Store (past Ramada signal), green, yellow the works
Mirror ball -> AV Tec, Salwa Road (Sales), Crystal Studios (Rental)
Reflector Tape -> Call Qatar Neon, they have the films that can be cut to shape

There is a crazy "headshop" in City Center, behind the Leisure land, in the corner. They have UV Lights
and other crazy things... they might have something like these...

Plankton