Sad to know about the robbery, however, we cannot avoid such things as it will keep on happening with increasing anti social elements found in our society. Well the best bet for you to find out the right option for your car is to try out a couple over the sites like Ebay. There you can find some of the best options, which can suit your budget and choice as well. All you need to do is to simply visit site and type the relevant keywords to embark with the right options. In fact, I often do this exercise and end up finding good options out there.
I guess buying a new car seat is always a better option than using a used one.
If you look on http://www.carseatvs.com/find
I think
Safety 1st Alpha Omega Elite
http://safety1st.djgusa.com/en/djgusa/safety1st/convertible-car-seats/alpha-omega-eliter-trade%3B-
convertible-car-seat-na
Safety 1st Alpha Elite 65
http://safety1st.djgusa.com/en/djgusa/safety1st/convertible-car-seats/alpha-elite-trade%3B-65-
convertible-car-seat---callie-cc081bnw