Thanks, this worked for me but I had to first identify to which table my attachment was attaching to when I add it on the catalog item form. It seems like it is same as record producer's table. 

Since I have my record producer on Incident table I ran your script something like below.

var sa - new GlideSysAttachment();
sa.copy('incident',current.sys_id,'request', 'SYSID of Request');

Thanks again for helping me out here.