R2-L3 can be seen rolling along in Mos Espa, only a few feet away from a fellow BAD, R4-J1. Both droids are in the streets before Anakin and Padme come upon Watto, during their search for the missing Shmi Skywalker. Source: Attack of the Clones.
Yeah, this is basically a copy and paste review for that R4-J1. It was a long month, don’t judge me!
What you need to build R2-L3:

BD36 Wioslea
BD8 Darth Vader

BD37 Trinta Duaba & Dice Ibegon Droid
BD16 Clone Trooper

BD34 Obi-Wan Kenobi

BD35 Pons Limbic
BD10 Clone Scuba Trooper