I have (3) extra Delphi 3-place GT-150 P2S (Pull 2 Seal) Male connectors left. I purchased a few of them for some friends and myself. This is the connector that you can attach to the Radio Shack siren and plug into the security siren connector [142] on a Harley.

You get the following:
(1) connector
(1) cavity plug (already installed)
(2) P2S (pull to seat) 16-20 gauge pins

$20 (includes shipping in US)