Are there any alternatives to ESO Fund for non-recourse cash advances?

I was an early employee at a private US startup many years ago. I exercised some stock options, but I cannot sell any shares yet due to transfer restrictions (which is quite common.) I am not a US citizen or tax resident, and I have moved back to my home country of New Zealand.

I have received an offer from ESO Fund [1]. They are offering to provide a non-recourse cash advance (aka a loan) in exchange for a percentage of the upside after the company has an IPO.

One of the conditions of this offer is that I would need to transfer my shares into a trust. This would be a Permitted Transfer, which the company does allow. I believe the purpose of the trust is to function as an escrow, to ensure that they receive their money after the IPO.

I've talked to a tax advisor, and this will cause some huge problems due to my country's tax laws (FIF.) We basically have a wealth tax for foreign investments, and this transfer would cause my annual tax bill to increase by hundreds of thousands of dollars. I cannot afford to pay these taxes because my shares are illiquid. I am currently exempt from this FIF tax since I received the shares through an employee share scheme (EX 38.) Transferring my shares to a trust would cause me to lose this exemption.

Can anyone suggest any solutions to this problem? Is there some additional clause we could add to the contract, or anything else I could offer them?

Otherwise, are there any alternatives to ESO Fund that might allow me to continue owning the shares?

Finally, this company is basically ready to have an IPO whenever the conditions are right. They could have had an IPO last year. How much longer do you think I might need to wait for the IPO?

[1] https://www.esofund.com