Hmm probably 2C-D and 2C-T-21 would be some of the main contenders.. Some of the tryptamines also have monoamine reuptake inhibiting action I believe, but typically more on the serotonin side than dopamine - and those compounds would really stress me out and do 100 different things before improving any cognition.
Modestly dosed lysergamides would also be an excellent choice probably, if you just pretend that you are basically using it as Hydergine.
Low dosed 2C-E is one that I actually wonder about what it would do for cognition, or if its cognitive effects are by far surpassed by meditative effects - whether meditative effects are excellent for cognitive tasks I'm inclined to assume but just as curious about..