The fastest might be to buy a few more miles, especially if the 100% Bonus on purchased miles is still going on. I would expect a couple days delay between any skymall merchant and US to credit the miles, but a purchase of US miles should hit your account pretty quickly (the bonus takes a little longer but the original miles should go pretty fast).
Not too much in the skymall catalog is cheap and I'm not 100% sure but I don't think you can buy items with miles, only buy items with money and get a mileage bonus.
Any acticity in your account will keep the miles alive. I'd be worried that buying a trip with miles and later cancelling it would come back to haunt you in the form of a retroactive mileage expiration. They also charge all members other than CP a mileage redeposit fee when you cancel, which is a lot more than the $40 keepalive fee.
Or you can just transfer them to me
I can find something to do with them!