Originally Posted by
maddog34
so i can use a 20 oz. framing hammer's claws?
or a bic pen ink tube? not the body of the pen, but the ink tube inside.... sans ink, of course...
a buddy used a trojan still in the package once...
sorry... couldn't resist....
or a folded up business card works well. use a couple zip ties or twist ties to hold it in place during shipping.

If you can shove it in there you can use it.
You'll have to use your own common sense on whether it will damage the pads, caliper body or anything else.
If you are going to be passing the bike on to me without the wheels installed, I might suggest you use $100.00 bills in sufficient quantity to make a thick enough layer to wedge in there!! <grin>
Getting back to suggestions for the OP:
Some bike shops might just have some laying around and give them away for free or just charge a pittance for them. Certain little things like this tend to accumulate where bikes are assembled regularly. I got my tool for plugging and unplugging Di2 wire free simply by asking at one of the LBS's here. He picked up half a dozen of them from nooks and crannies nearby in his shop area before finally handing me one. Not sure what he was looking for but I saw no damage on the one he gave me, and free is free so I wouldn't care if it was scratched or dinged.