Thanks to a tip-off on the excellent Marooned: Science Fiction, Fantasy and Horror books on Mars blog, I have been viewing some complete issues of old science fiction pulps magazines on the Internet Archive. These are magazines which have (allegedly) gone into the public domain due to non-renewal of US copyright in the past.
Of the magazines currently online (put there by one Gerard Arhus), there are two which contain Bradbury stories. Planet Stories volume 4 number 6 (spring 1950) contains the first publication of Ray Bradbury's story "Forever and the Earth". Planet Stories volume 4 number 8 (fall 1950) contains Bradbury's "Death Wish", perhaps better known under the variant title "Blue Bottle".
The full list of pulps uploaded by Arhus can be found here. My top tip is to use the "read online" option, as this is quicker than waiting for the PDF versions to download.
It's quite fascinating to see these stories in their original context. In a sense, it's an "accidental" context: Bradbury didn't write these stories to order, and didn't write them for this particular magazine; instead, he would write his stories for himself and then send them out to a range of publications. But it's worth bearing in mind that the garish covers and hokey stories by other writers that surrounded his stories were part of what created the label of "Ray Bradbury is a science fiction writer", a label which he fought many years to shake off. And a fight which continues today!