Here are two lemon pie recipes made with whipped topping. The first is an adaptation of a Dream Whip strawberry pie recipe I clipped from an ad some years ago. I hope you can use one of them.

LEMON DREAM PIE
1 (4-serving) pkg. vanilla pudding mix (cook and serve type, not instant)
1 (3-oz) pkg. lemon gelatin
2 cups water
2 tablespoons lemon juice
1 teaspoon finely grated lemon rind
1 1/2 cups prepared Dream Whip topping
Cooled, baked 9" pie shell OR graham cracker crust

Combine pudding mix gelatin, water, and lemon juice in saucepan. Cook and stir over medium heat until mixture comes to a boil. Add grated lemon rind. Pour into bowl and chill until thickened. (To hasten chilling, place bowl of pudding mixture in larger bowl of ice and water; stir until thickened. Blend in prepared Dream Whip. Pour into pie shell; chill until set, 1 to 2 hours. Garnish with additional whipped topping.LOUISIANA LEMONADE PIE
1 8-oz carton frozen whipped topping (Dream Whip could be substituted)
1 (6-oz) can frozen lemonade concentrate
2 tbsp. fresh squeezed lemon juice
2 tsp. fresh grated lemon peel
1 (14-oz) can sweetened condensed milk
1 9" baked pie shell

Without thawing topping or lemonade, put all filling ingredients in large bowl. Beat with electric mixer at low speed until thoroughly combined. [If using Dream Whip instead of frozen topping, I would fold it in after beating the other ingredients.] Switch mixer speed to high and continue beating for 3 minutes.
Pour filling into crust. Chill for several hours before serving, or freeze if desired.