The commercial truck dealer in Cotati (Redwood Reliance ) sells Locomotive style air horns for semi's . Keep in mind every parked locomotive on the NWP has had its air horn ripped off. Some were taken while the railroad was still active. Angle iron was even welded over the head of the bolts of the horns so they could not be unbolted without some effort. Most of the bells, builders plates and ever number boards are missing too.