When you start on the solicitation trail for silent and live auction items, you can use the incentive of your attendees demographics to help you get a "yes" by having the person you're asking take off their charity hat and put on their marketing hat! Most of the businesses that you approach have gone through their "charity' budget long before you got there, but there's always marketing funds in reserve throughout the year. Have a breakdown of your demographics handy and emphasize that the couple of hundred people who attend your event consist of those who are already customers and those who may be, after seeing your support for their organization. I also suggest that "who" asks will certainly make the difference in how the ask is received. If one of your solicitation team members has a personal or customer based relationship with a prospective donor they should be the one to ask.
It's also important that you try and target the ask by knowing what you actually would like from the donor, so that you don't get into the "what do you want"...."what do you got" conversation. If you need the donor to contribute something that's part of a great auction lot, let them know that. A well thought out ask shows a lot more respect for the donors time and resources than "gimme something"