The only risk with making your own pear juice is the high pH of the juice, and the fact so2 doesn't work so well due to binding by acetaldehyde found in pear juice - probably why straight pear juice isn't sold so often. I have lots of pears I will be juicing at Bathurst, I have a nashi covered in pears I probably won't even use. The juice is nice but not a lot of flavour, the best thing is the unfermented sugars give it a bit of body.
where are you? if your in melbournes east you can get filtered pure pear juice from the orchard on maroondah hwy just outside coldstream heading towards healesville. im pretty sure wild about fruit in chirnside park make it too.
You could try all apple juice but ferment quite cool with recultured coopers bottle yeast to chuck pear ester which is ETHYL 2,4-DECADIENOATE and is responsible for the aroma of pears. You could maybe see if your local distilling supplies -oops sorry I meant LHBS stocks a pear essence.
No shame in using an essence, Choc hazelnut porter brewers do it all the time.
If you want to use pears for the sweetness, back sweeten with something artificial or with lactose.