Here's the deal ... Justin bought some fresh Kobe-inspired artwork from Idiot Box Art owners Emily Bright and Tamara Martin, and then the artists started making and selling miniature versions for $200 a pop, with 24 percent of the profits going to the MambaOnThree Fund.

The cartoon Kobe art is pretty cool ... it's a teddy bear wearing a Mamba hoodie under Kobe's #8 Lakers jersey, palming a basketball and rocking some of Kobe's signature Nikes.

Justin dropped $1,200 for a bigger piece -- one of only 5 ever made -- and hung it up in his crib next to some skateboard decks.

Lots of folks apparently share Justin's eye for Kobe art ... because Idiot Box ended up selling 260 mini Mamba bears during a 2-day limited sale, which was enough to make a $12,480 donation to Kobe's foundation.

MambaOnThree was created to support the families of the 7 other victims, besides Kobe and Gigi, who died in the crash.