Shameful to admit this, but I've had to resort to Starbucks on a few occassions over the last 5 years to tide me over in-between shipments and when I was out of greens to roast myself. I'm more cautious and observant now.
Having said that, IF you decide to go the Starbucks route, I recommend their House Blend as a decent alternative. While it will not be stellar, it is very drinkable, but you'll have to tighten your grind a bit as the beans will be older that what you are accustomed to using, otherwise you'll have a 10-second or less shot. Also, like Jonny said, their beans go stale very fast, so hopefully you only need a few days worth at best.
Avoid their Espresso Blend as it's basically aged tar and will have so much oil present you'll want to clean your grinder to remove the contamination it leaves behind.
Good luck, and let us know your outcome.