I've never used a strawberry lemonade, but I have a raspberry lemonade from WSP that is absolutely awesome. It smells so realistic you'll be temtped to drink it. It does great in CP, too. This is only my opinion so take it for what it is worth, but I believe it would substitute very nicely for strawberry lemonade.
I found this on pinemeadows recipe section. At the very bottom they have scent blend recipes: Strawberry Lemonade
2 parts Wild Strawberry F.O.
1 part Lemon Squeeze F.O.