Amanda, is it not possible to make a deposit into the bank that the seller has provided account details for ? I have done this before internet banking and smart phones became mainstream. You just go into the bank of the seller eg if his bank is ASB then go to the closest ASB branch for you and ask to make a manual deposit to the persons account, provide the Name if known and account number.    

Just keep an eye on the auction people like to outbid an auto bid at the close, Auto bid isn't a guarantee you will win. It just makes it easier when dealing with those people who like to let the time run down then bid at the last second, then repeat the process another 10x 

Tell them you were running a straight up auction no shill bids, if they don't like the price they shouldn't have bid, you probably better off just offering the item to the second highest bidder anyway and leave bad feedback on the Top bidder for not following through