Following the largest initial public offering (IPO) in history, Space Exploration Technologies (SPCX +2.83%) stock is starting to pop up in a variety of exchange-traded funds (ETFs). The number seems to increase by the day.To be precise, the stock in Elon Musk's reusable rockets company is a constituent of 148 ETFs as of July 3. The stock is a top-15 holding in 35 of those funds. Market participants looking to leverage ETFs as proxies on SpaceX stock have plenty of options to consider. There are actively ma ...