You can purchase shares through a company such as Sharespost or Equityzen. I am not sure if there are currently any shares for sale, but those are sites to visit. I purchased shares in Ripple last year through Equityzen and the minimum investment size was $20,000 to participate. Sharespost has a minimum of $100,000 investment so that could work for you. Each company will allow you to be put on a waitlist and will contact you if shares come available and then let you know the time and date you can invest. When I purchased last year it was around the time a few employees left the company to start Coil so I assume I purchased a block of their shares they were liquidating. I hope this helps.