If your securities are not publicly traded there is no legal way to sell options on them. About the closest you could come would be some sort of proposition bet which is illegal in pretty much every state of the USA. And as I mentioned before, at the end of the day your "stock" in a privately funded company, is simply a ledger entry on a spreadsheet somewhere. And without the active participation of the CFO/Controller/accountant/and-or/Counsel there is no way to durably transfer ownership to anyone.

That said, I don't doubt that you might find someone with excess cash who would be willing to front you the money to exercise your stock and pay the taxes and a perhaps a premium on the stock, for a promissory note to hand them over the stock at the time it becomes publicly traded. That too it illegal under securities law but would be fairly difficult to prosecute.