Will you accept a sherbet instead? This is from Julia Child. I made it once with my little sister. It's not difficult.
It doesn't use weight, alas, but you puree the pears, so just stop chopping when you get enough.
3/4 c. sugar
1 egg white (fear not!)
3-4 T. pear liqueur (optional)
Grate the rind of the lemon into a large bowl. Strain in the juice of both (you want about 4 T.).
Peel, quarter, and core the pears, then cut into chunks. Put them in with the lemon juice and toss to coat. Sprinkle with a bit of sugar. (Do this as you go along. It will prevent discoloration.)
As soon as they're ready, pour into a food processor with all of the juice and the rest of the sugar and puree. When it's smooth and the sugar is dissolved, add the egg white and puree for awhile longer.
(If you only have a blender, you'll need to beat the egg white in a separate bowl until soft peaks form, then fold in the puree).
Put that bad boy into your ice cream maker and process as per manufacturer's instructions.