There are some reference books that could help you, like,
Bloody Murder by Julian Symons -- out of date for newer writers, it would still help with older writers in the Agatha Christie/Dorothy L. Sayers tradition;
Talking about Detective Fiction by P. D. James -- would perhaps help with newer writers; she taps into Symons book for information on the older ones;
Crime and Mystery: The 100 Best Books by H. R. F. Keating -- Keating was a mystery writer of some repute from the 1960s into the 2000s. This is a decent reading list of which some would fall into the cozy category.
"Cozy" is either defined so narrowly (elderly spinster solves murders while knitting with a cat on her lap who may or may not talk to her) or so broadly (not hard-boiled) that it's tough to discern what definition comes closest to your need.
Among older writers, look for Agatha Christie, Dorothy L. Sayers, John Dickson Carr, Marjorie Allingham. Recently two sources of older mysteries seem to be doing well in the American market:
American Crime Classics and
British Library Crime Classics. More recently,
Poison Pen Press has started working with the Library of Congress to reissue some older American mysteries. A lot of the titles, particularly in the British Library books, are not hard-boiled, and some could be considered cozies.
P.D. James's series is interesting (Ruth Rendall's, too, probably though I haven't read them) because they updated the Christie/Sayers tradition for the 1960s-'90s. I need to read more of James's work to get a real feel for it, but the first novel,
Cover Her Face is really good first novel, not a scene wasted, offering both a good, solid mystery and an examination of the aristocracy post-WWII.
I second Louise Penny, mentioned above, and would add Donna Leon. Neither are hard-boiled, but neither is exactly cozy, either, I think. But both are very entertaining. About Leon, her series is based in Venice and since I doubt I'll ever get there, it's a pleasant trip abroad for me. Well, except for the murders, of course.
Honestly, if you just search for cozies at the website of your favorite book seller, you'll find there are tons of them. I suspect the quality is variable, just as with hard-boiled and others, but read a few any maybe you'll find an author or two you like and then you can work from there with the "if I like this, what else might I like" question.
Randy M.