Finding Catalytic Converter gaskets
 

I just converted my 2000 honda civic LX's exhaust to a 2.5" catback (not finished yet) ... Here it is: Honda Accord 2 2L Honda Civic 1 6L UltraFit Exhaust CC1144 Catalytic Converter | eBay ... I emailed the company and asked what make and model I should ask for at autozone so the could find the correct size gaskets for it ... They did not help... at all...ridiculous ... anyway, At autozone we tried some from an Accord EX and a Civic EX ... none fit. Anybody know how I'd go about measuring and finding the correct gasket rings??? And also, should I use flange type gasket also for it??

Right now, I have taken off the old catalytic and downpipe and muffler system, and now have the headers, down pipe and new cat on it, over the oversized donut that came with the header/downpipe order. Here's the items I bought, someone please help!! -

Catalytic Converter: Honda Accord 2 2L Honda Civic 1 6L UltraFit Exhaust CC1144 Catalytic Converter | eBay

Header/Downpipe: M2 Performance Stainless Header Downpipe Combo 1988 2000 Honda Civic D15 D16 | eBay (this came with a donut gasket [not in the picture] that doesn't fit in the cat.. grrrr)

(I don't think I need to post the catback exhaust I bought)