Keep items in the backpack, even when player dies?

So the player will purchase an item from the shop, which needs to be given to the player in such a way that it will stay in the backpack, even if they reset.

Backpack doesn't work, because it resets when the player dies.

Also, StarterGear doesn't work, because then every player will get the item.

I'm stumped...

Here's my code (temporarily using the Backpack):

leaderstats = game.Players.LocalPlayer:WaitForChild("leaderstats")

function onClickEvent()
	
	print(game.Players.LocalPlayer.Name.." is attempting a purchase.")
	
	if leaderstats.Tokens.Value < 0 then
		
		print("Not enough tokens!")
		script.Error:Play()
		
	else
		
		print("Ok!")
		leaderstats.Tokens.Value = leaderstats.Tokens.Value - 1500
		
		local purchasedItem = game.ReplicatedStorage.Items.ClassicLauncher:Clone()
		
		purchasedItem.Parent = game.Players.LocalPlayer:WaitForChild("Backpack")
		
	end
	
end

script.Parent.MouseButton1Click:Connect(onClickEvent)

I suggest you :Clone() items from ServerStorage into the player's backpack after they die, aka when their character loads.

-- server script in ServerScriptService

local boughtItems = {
	game.ServerStorage.Items.Item1;
	game.ServerStorage.Items.Item2;
}

game:GetService("Players").PlayerAdded:Connect(function(p)
	p.CharacterAdded:connect(function()
		for a,b in next, boughtitems do
			b:Clone().Parent=p:WaitForChild("Backpack")
		end
	end)
end)

You should clone the tool to the backpack, plus another one to THAT players starter gear.

leaderstats = game.Players.LocalPlayer:WaitForChild("leaderstats")

function onClickEvent()

    print(game.Players.LocalPlayer.Name.." is attempting a purchase.")

    if leaderstats.Tokens.Value < 0 then

        print("Not enough tokens!")
        script.Error:Play()

    else

        print("Ok!")
        leaderstats.Tokens.Value = leaderstats.Tokens.Value - 1500

        local purchasedItem = game.ReplicatedStorage.Items.ClassicLauncher:Clone()
local purchasedItem2 = game.ReplicatedStorage.Items.ClassicLauncher:Clone()
        purchasedItem.Parent = game.Players.LocalPlayer:WaitForChild("Backpack")
purchasedItem2.Parent = game.Players.LocalPlayer:WaitForChild("StarterGear")

    end

end

script.Parent.MouseButton1Click:Connect(onClickEvent)

and btw, you should do these things on client side. Only the client would see the leaderstats change. You should use remote events to make it seen to the server.

local savedBackpack = {} -- Creating a table for our backpack, we'll iterate through this later.
local Player = game:GetService("Players").LocalPlayer

-- When the user purchases an item,

local purchasedItem = game.ReplicatedStorage.Items.ClassicLauncher:Clone()
purchasedItem.Parent = game.Players.LocalPlayer:WaitForChild("Backpack")
table.insert(savedBackpack, purchasedItem);

-- When the player dies,

for _,v in pairs(savedBackpack) do
	v.Parent = Player:WaitForChild("BackPack")
end

Please for the love of god use tables for this, don't parent anything to a storage like others have sugguested.

--put in ServerScriptService
local Storage = Instance.new("Folder")
Storage.Parent = game:GetService("ServerStorage")
Storage.Name = "Storage"
game:GetService("Players").PlayerAdded:connect(function(plr)
	if not Storage:FindFirstChild(plr.Name) then --Creates player storage
		local Folder = Instance.new("Folder")
		Folder.Parent = Storage
		Folder.Name = plr.Name
	end
	plr.CharacterAdded:connect(function(char)
		for i,v in pairs(Storage[plr.Name]:GetChildren()) do --Loads player data
			v.Parent = char
		end
		char.Humanoid.Died:connect(function()
			for i,v in pairs(char:GetChildren()) do --Saves player data
				if v:IsA("Tool") then
					v.Parent = Storage
				end
			end
		end)
	end)
end)
game:GetService("Players").PlayerRemoving:connect(function(plr)
	pcall(function()
		Storage[plr.Name]:Destroy() --Removes player data
	end)
end)