credit unions and other financial institutions usually offer bulk shredding after April 15th and through the early summer, so you might check where you bank. Also, they may allow you to bring a bag or two to their branch.
WSB usually lists an event like this in the calendar and/or on the home page. I searched the blog and the calendar and it seems as if this year’s events have already happened, but there may be more in the fall if you’re not in a hurry.