[Brad Winder]

I don't recall hearing of any transistor car radios being offered to the public before Chrysler brought one out in 1955. But there probably were experimental models being played with between 1948 when the transistor was introduced and 1955. They likely would have been very expensive, had they gone into production.

From Wikipedia:Chrysler Mopar 914HR

1955 Chrysler – Philco all transistor car radio – "Breaking News" radio broadcast announcement.
Chrysler and Philco announced that they had developed and produced the world's first all-transistor car radio in the April 28th 1955 edition of the Wall Street Journal.[15] Chrysler made the all-transistor car radio, Mopar model 914HR, available as an "option" in fall 1955 for its new line of 1956 Chrysler and Imperial cars, which hit the showroom floor on October 21, 1955. The all-transistor car radio was a $150 option (equivalent to $1,710 in 2023).