www.sharespost.com has very recently helped facilitate indirect investments into SpaceX via Funds setup solely to buy/hold SpaceX shares. Of all private companies Sharespost transacts in, these opportunities to indirectly invest in SpaceX are by far their highest demand and come and go quickly (e.g. must be prepared to act very quickly on paperwork and funding when opportunity comes up).
While these opportunities do come up occasionally with SharesPost, because it is in such high demand(relative to supply) their fees are non-negotiable (e.g. 5% commission) and the minimums are typically much higher if you want a realistic opportunity to get a piece (e.g. $1mm or more I would say is realistic).
Can do this individually, or some people will have their own LLC setup with a group of 10 friends for example who each put in $100k to make it $1mm in total and then use that LLC to invest the $1mm via Sharespost for example.
PM me if interested given above and I can make an intro to my senior contact at Sharespost so they can keep you in the loop for if/when they see next opportunity come up.