Any carrier that writes business in the "transportation" industry can easily accomodate you. I'll list some I know off the top of my head. Acuity, Auto Owners, Northland, Great West, AIG(chartis), National Interstate, Sentry, Progressive, Chubb,Harco, and there are many others.
You could also look into the safer stat DOT website for information on an MCS90 form.