After modifying my GS3, I have some spare parts available. They are used parts and were functioning well when I removed them. Prices include shipping to CONUS. Located in Bay Area if you are local.

$130 - GS3 Panels - Both panels in very good condition, light scratch on left panel
$40 (SOLD) - Steam Pressure Gauge - Very good condition
$40 (SOLD) - Brew Pressure Gauge - Very good condition
$70 - Steam Valve (w/ 2x pipes, mount) - Good, valve may benefit from a rebuild

Detailed album here