Similar to its 3e version, but instead of it being a replication, its just something for druids to enable battle druids who are not your typically furry shapeshifters and instead just something akin to a battle cleric.
https://www.d20srd.org/srd/spells/shillelagh.htm
Make it spell level 3.
It allows a druid who casts it to have full APR akin to divine power as well as setting "legal weapons" on a scaling enhancement that goes to to 4 (1, 2, 3, 4 scaling), even if its already enchanted.
The weapons are club, greatclub, quarterstaff, maul, magestaff so long as they are made of natural materials or tagged to be legal with the spell despite that.
Potentially could add all "druid proficiency" & unarmed (unless you are transformed or a monk) weapons as long as they're made of natural materials, but they don't get the +4 scaling enhancement which may allow more larp.
Duration I couldn't really care about, I think turns would be fine because even in the broadest sense it would only apply to a scimitar and a battle druid is never going to be optimal unless someone does a horrifying thing.
Shapeshifting should cancel the spell.