This is a sad story: 90-day exercise windows are employee hostile, they should be much longer, especially when the company isn't public.

However, and I don't know how to put this more kindly, but I can't help but wonder if you understood how options work while employed at the company?

A simple technique to avoid having to quickly come up with a lump sum is to set aside enough money to excercise your options as you accumulate them.

In this case putting aside $4,250/year earmarked for exercising your stock options would have allowed you to save the $34k required.