Kahr CW45, P45, or TP45. All DAO, all single stack, none of them Glocks.
I'm big on Kahrs, so I'll let others come up with alternatives.
-edit-
The only one of my suggestions you'll find for less than $500 (new at least) is the CW45, but it gives up nothing in terms of reliability to the others.
The Kahr's aren't Double-action - they just have a very long stiff trigger - once you drop the striker, you can't pull it again.
The Sig P220 is a classic (and if you're in the polymer camp, but not a glock fan, check out the HK or FN 45 models).
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