I do not believe they exist, your question states the reason why this so. The number one rule with slow cooker, put nothing frozen into it. There is no guarantee that goods you put in frozen in the AM would be unthawed by the time the cook cycle started. And do trust me, if you tried this once, you would not want to eat what came out of that slow cooker. If you wanted to try, get an older one that has off, low and high twist knob, plug that into a timer and set the timer for start time and set cook temperature and go for it. Make sure there is a Hospital close by.
Or, you could simply get a slow cooker like I own. I set the cook temp, the time and when it done cooking, it will stay warm until I unplug it or turn it off. We can set it up at 7 Am, cook on low for 7 1/2 hours, come home at 5 and have a hot meal waiting for us. Ours is a GE unit from WalMart,. They are to found everywhere.