Well, itd be pretty simple, create an ability based on the item stat gain bonuses (if your ability has multiple levels, give it multiple levels as well) set it to give as much as you want the aura to give, then youll have to use some triggers:
Event: Every 0.01 seconds
Condition: n/a
Actions: Pick every unit inside (AoE of ability) of (unit with ability) and do actions
If/Then/Else multiple functions
->Condition: If picked unit has (stat gain ability) equal to false & picked unit is a hero equal to true
->Then: Add (stat bonus) to (picked unit)
------> Set level of (stat bonus) for (picked unit) to level of (Aura) for (unit with Aura)
->Else: Do Nothing
To remove the effect:
Event: Every 1 seconds
Condition: n/a
Actions: Pick every unit inside (playable map area) and do (remove (stat bonus) from picked unit)
That should work, and it wont stack, even though the 2nd event removes it from all units, the 1st trigger runs more often, so as soon as it is removed it will be readded.