If you are seriously looking forward to running this signature campaign I would suggest you to use escrow with funds for at least 1-2 weeks. As far as I'm concerned you can lock deposits and withdrawals on any accounts.
That is no problem. I can do this for everyone who wants this.
So then, who will you be using for escrowing that amount? You should only start this thread after you get the confirmation from the escrow that he has the control of the funds.