Found 3 alternatives for PD2401 by IXYS Integrated Circuits Division. Solid State Relays — 16-DIP (0.300", 7.62mm), 4 Leads.
SSR RELAY SPST-NO 1A 0-600V
SSR RELAY SPST-NO 1A 0-500V
SSR RELAY SPST-NO 1A 0-400V