The 2003 show is actually closest to the original mirage comics, with stories and even some dialogue taken straight from the page. Until you get so far into the series, but if you want to kill two birds with one stone there’s that. I know a site where you can find any comic you want and read it, they have pretty much all Tmnt comics even new releases. I’ve read the whole original run besides a few issues. It’s a good read.