You could try using pear juice in the intial blend.
I'll qualify this by saying I haven't actually brewed a cider, but I've been thinking about doing one and doing a bit of research. What I can gather is that some fruits contain a small percentage of sorbitol, a non-fermentable sugar, as well as the fermentable glucose and fructose. Thus the amount of sorbitol in the juice to be fermented contributes to the sweetness (or otherwise) of the final fermented beverage.
Apples are generally low in sorbitol, while pears can have a much higher proportion of their overall sugar content. I guess that's why pear juice works as a back sweetener for bottle carbonation.
I've also read that sucralose can be used to back sweeten. I think that's an artificial sweetener and I'm not keen on them personally.