OK... I have given this some thought...
What you essentially want is something a bit sweeter than fully dry. Apples don't actually have much flavour beyond sweet and acid so when most people say "apple flavour" what they usually mean is "a bit sweet". Th eissue of course is that apples are all simple sugars so pretty much any yeast will leave them completely dry.
There are two things we can do - add some unfermentable sugar somehow or stop the yeast before it finishes.
We'll look at stopping the yeast first. To do that we need to either kill it or remove it. Killing can be done with pasturisation or some sort of chemical. Removal usually means sterile filtration. The issue with both methods is that usually you have to do it before the cider is carbed. You can't bottle condition then uncap, add some chemical and re-cap. Well I suppose you could but its a hell of a lot of work and adding the chemical to carbed cider will probably lose most of your cider to gushers. Likewise with filtration. You can't filter carbed cider and by the sounds of it you don't have the gear for that. You also don't have the gear the force carb still cider so for the moment lets' rule out yeast removal as an option.
That leaves us with unfermentable sugars. Fortunately there are plenty the we can choose from. Lactose is the most common one but no good if you have anyone lactose intolerant. Its also not very sweet so you do need to use quite a bit. Maltodextrin is also another option. Its only partially unfermentable so you will end up with stronger cider. We could add some complex sugars by adding malt but then you wind up with a graff not a cider and it will start to taste a bit beery. It will also make it stronger as you are again adding fermentables as well as unfermentables. If you don't mind stronger cider, there are other compex sugars we can add - brown sugar, rappidura, etc all of which will add flavour and some residual sweetness.
The last option for adding unfermentables is to add pear juice. Pears contain a sugar called sorbitol which is unfermentable. So replacing a percentage of your apple juice with pear will add some unfermentable sorbitol without making the cider stronger as you are replacing juice with juice rather than adding a sugar to juice. How much pear? Depends on the variety but you could start with 10% and experiment from there.
The last thing we can look at is yeast. All yeasts will leave a cider dry but some will produce esters along the way that give a "fruity" flavour which will increase the perception of sweetness in the cider. Using a fruity ale yeast may (and I say may because the nutrient and precursor chemical balance are completely different in juice compared to wort) increase perceived sweetness. There are also some wine yeasts that will enhance fruit flavours but their effect is much more subtle than a beer yeast although they are designed to work in a juice environment (different juice but still more similar than wort) so they may actually work better. Have a look in your local brewshop and see what they have. Unfortunately, most of the really interesting wine strains are only available in bulk kilo packs for professional use.
Ok... so a recipe.
Lets go for 90% apple juice and 10% pear. Ferment with either a good wine yeast that enhances fruit or an ale yeast. After fermentation, you can taste and add lactose to bump up the sweetness further if necessary. You will also probably want to add a little malic acid to bring things back into balance. Add a tiny bit, taste, add more. Stop a little short of where you think it needs to be as its really easy to overshoot.
Give something like that a go and start tweaking. It will take a while to dial in exactly what you like. You may need to add more pear or less pear or you don't like the esters from the yeast so need to try a different one. Each batch change one thing (only one thing so you know what made the difference) and start to bring it closer to what you are after. You can post your experiments and help others learn from what you are doing.
Cheers
Dave
