headers and cats.. help

[the barber]

So yesterday I decided to do my rear cat removal, my self, needless to say I should have waited for an experienced welder. Long story short F'd up the welds and had a buddy re-weld them no leaks and now I do believe I have a leak where the header and cat connect and have been looking for the gasket or something to fix this problem does n e one have n e insight on-the-job part I'm looking for or a solution? Thanks in advance Alex.