This thing literally happen to me and fixed it for under 1k with Smog check and Registration since mines was expiring soon!!! In California also with 2005 Accord with EFC# 5HNXV02.4ECV.

If you're in California you can have a Smog Referee validate the aftermarket catalyst converter for your vehicle and getting the BAR Label which allows you to use aftermarket Cat at Smog Check stations. Here's the link that explains everything(they literally added more aftermarket cats on July 6th) and a video explaining it. You can get the Walker 82895(on the Acceptable Catalytic Converters list and the cheapest :D), Front Gasket, Downstream O2 Sensor(the one that goes into the Cat), Upstream O2 Sensor(the one before the cat in the pipe)(yes you gotta replace both of the O2 sensors), then you'll have to get the upper18182-RAD-L11.aspx)/bottom18181-RAD-L11.aspx) cover along with all the 3x front screws__18176-PT0-003.aspx). If they also cut the pipe going to the resonator which they most likely did then use this(includes Rear Gasket and screws so the only screws you buy is the front screws), then weld a pipe between that part and the left-over pipe so you don't have to replace entire muffler exhaust system. If you have no welder then a Muffler Shop should do this for you once you installed the cat and only thing left would be the pipe.

All the parts I've listed literally cost $613. You can do your own research and what situation your exhaust system in the vehicle is in. The parts I've listed are what I did for my specific vehicle since the thieves did not touch the front pipe before the cat on my vehicle and I bought front screws since old ones were rusted. You'll have to quickly do Referee Scheduling because they(Smog Referee) could at anytime no longer allow you to install aftermarket Converters to SUEV Accords. Last I've heard OEM cat is still months on back order so you still got time. Once it's installed that's it you'll be able to hopefully pass the Catalyst verification portion of the smog check every 2 years as you have the BAR Label to validate the use of the cat converter for your car and you don't have to install an OEM Cat next time you do a Smog Check. You won't have to replace it down the line unless it gets stolen again or the cat failed.

Hope this helps you and any future "unfortunate" people reading this.