"Several real estate agents have said no to listing it for me because they either don't want to go that far, or because they don't deal in vacant land".
A broker does not really need to visit vacant land as often as they would, say a house. They just need a survey, tax id#, and a few other key pieces of information and can send prospective buyers there unaccompanied, then right up offers.
If you want to cut out the middle man, you could post a sign there with your phone number and fax a survey to interested buyers. Negotiate over the phone, maybe type up a letter of intent, then turn it over to your attorney (probably a local near the land) and have him/her workout the details with the buyer's attorney. You may or may not have to show up for the closing at the title company.