Even if an actor doesn't have their own prod co., I would still query them and see if they want to attach to the script.
This can work for your benefit, since many prod co's (especially those with studio shingles) like to see a package, including attachments from actors and directors.
This can also be a disadvantage for you, if the prod co who thinks of buying your script has someone else in mind, or if you attach "b" or "c" list actors that a prod co could care less about.
The important thing is to generate interest and get your work read. Enough people read it, it is bound to get interest or noticed-- law of averages.
If an actor likes your script, they tell two friends and they tell two friends...
I know a writer who queried and got an "A" list actor to attach to his script, who in turn got an agent because of the mention of that attachment in his query, who in turn got a director on board, who in turn got a producer (who incidentally was cold queried that same script a year earlier and didn't request the script) to option it. Last I heard, the script is close to getting greenlit.
Of course the script has to be good, otherwise, the actor, agent, director and producer will pass.