This divider is specifically made for the Plano 3500 series organizer. Plano does not make additional dividers available so I've made some compatible dividers that anyone can make or order.
Amazon link to organizer:
http://smile.amazon.com/Plano-Molding-Company-Prolatch-Stowaway/dp/B00CKIG4NC/ref=cm_cd_al_qh_dp_t
Have a 3D Printer? Make it yourself:
www.thingiverse.com/thing:934472