There are two types of options to step a mast single-handed. Several companies offer single-handed systems, typically using a trailer winch and a gin pole. Murray's (
www.murrays.com) is a good source for this sort of stuff. This option is fairly complicated (read: expensive).
The other option is using the jib halyard (if you have one) to hold the mast once you've raised it. If you don't have a jib halyard, it should be possible to devise another method to "sheet in" the forestay as you raise the mast.