One option, is to simply take the risk. You're going to get back 250K immediately, and not having the rest means either some scrambling and negotiating with your investors and creditors, or maybe worst case going out of business. There are other events that could lead to this too, and hedging against them all is impossible. So one could just accept that shit happens.

Getting a credit facility at another bank, during good times, is the other obviously one that I didn't see mentioned. Most of the money is still there in this case, it's a question of short term cash requirements.