Including shipping, this is probably about as cheap as making it yourself:
http://cgi.ebay.com/ebaymotors/NXS-MANUAL-BOOST-CONTROLLER-300ZX-GSX-GST-STI-RX7-MBC_W0QQcmdZViewItemQQcategoryZ33742QQihZ016QQitemZ260228635515QQrdZ1QQsspagenameZWDVW
Also, for the pop off, just shim it. Drill the center rivet out, disassemble it and and some washers to shim it and make it harder for it to open. Mine's currently set at 12psi as I used to run 10 unintercooled.
Mario