Exactly. Rather than have Warmoth accomodate the way you've chosen to hide money, you should move it. Getting them to take a method of payment hasn't been a problem.
As for hiding money. I kind of do. 5% of my paycheck goes to a vacation account at my credit union. Besides paying for vacations, it has bought new tires, Christmas gifts, etc. My wife and I have a joint checking account, so it makes it hard to surprise her sometimes. Also, being in the electrical trade, some contractors are more frugal than others with the disposal of scrap wire. I actually payed for my first Warmoth completely with scrap wire. It took a while, but it was faster than picking up cans. My wife didn't mind one bit because it was all legit and the bank account didn't feel it.