I thought the first filter was just SS mesh inside and re-usable. At least thats what Fleetguard Techline told me when I gave them the number.
You might try NAPA for their GOLD filters. Our Vol Fire Dept buys the Napa version for our ISC8. 3 truck (FS1024 I think). They are made for WIX (Napa Gold) by Fleetguard. Has the Stratopore emblem right on there. And Napa's filter hotline confirmed the drawing of the filter has notes refering to the Fleetguard manufacturer. The ISC8. 3 is so picky that Napa simply chose to rebadge the best filter to avoid a problem. This ISC CAPS injection pump can suffer fatal damage from even the smallest particle. So anything less than Fleetguard is a compromise. Even Napa agrees.