[amsat-bb] Landwehr preamp

Hi all.    I wonder if there is anyone out there who can help me, I am trying to locate a GASFET for my Landwehr 70 cms preamp model GAAS 435ma. I have been informed that there is no equivalent as these were specially for Landwehr Electronics so it would seem that my only hope is that someone, somewhere may have a preamp that has seen better days, but still has the Gasfet intact.   I have emailed Landwehr but to date no reply,   Any assistance would be greatfully appreciated. 73. Howard. G0VBT.