i have a 3.5 litre one with low/high/auto settings. swan - dont think they make them any more as about 25 years old. i think this size would suit you. just go for something cheapish, then if you don't get on with them it doesn't matter. i don't think it makes much difference anyway
I have been through four over the last week! Got a Morphy Richards one, the build quality was terrible, tried two identical Crock Pot ones but both were damaged, so ended up with the basic Tesco £14.99 one, looks really good, am just trying it out for the first time but seems like it's working quite well.
I've got two slow cookers that I use, an expensive crockpot 5.7ltr which is faultless and a cheap Tesco 3.5ltr which is faultless. I also have a breville which burns everything as it runs too hot for slow cooking and a morphy. Richards which has a lid default. -- outs self as a weird slow cooker hoarder-- I'd plump for a cheap Tesco one in your situation.