How about;
Dulled Sword
+5 Damage
+3% Lifesteal
Unique Passive; Every time a minion dies near you without you killing it, you gain 1 gold. Inflicting physical damage to champions grants 3 (5 for melee) gold once every 5 seconds.
Fake Sword
+10 Damage
+25 AA range (Ranged Only)
+10 MS (Melee Only)
+6% Lifesteal
Unique Passive; Every time a minion dies near you without you killing it, you gain 2 gold. Inflicting physical damage to champions grants 6 (12 for melee) gold once every 5 seconds.
Withered Sword
+35 Damage
+50 AA range (Ranged Only)
+20 MS (Melee Only)
+10% Lifesteal
Unique Passive; Every time a minion dies near you without you killing it, you gain 2 gold. Inflicting physical damage to champions grants 6 (12 for melee) gold once every 5 seconds.
Grants a nUnique Active;earby champion 25 (+0.3AD) bonus physical damage on-hit for 5 seconds; cannot be cast on self. (40 Seconds Cooldown)
AD champions don't have a support item. This is just my hunch on how it could work. It promotes poking at a steadier rate than Spellthief's (but lower, or riskier) while pretty much preventing it's use by AP champions, but discourages last hitting to maximize gold output to the lane. I'm not sure about the gold rate gain of course, but numbers are just numbers, it's easy to tweak.