The way I keep my devious Alden habit under wraps is with the paypal mastercard. You can use the mastercard just like any other regular credit card but the funds come from your paypal account and there is no bill. I deal with a decent amount of cash at work with travel, reimbursements, etc. so whenever I get cash I go get a greendot card and use it to transfer funds to my paypal account. From there I just have the shoes shipped to my office and it's done.
Of course my wife is aware of the overabundance of shoes/boots in my clauset. She just doesn't know exactly when a new pair shows up.