Avocado Tree in a large greenhouse

[RoudyRick]

HI all.  I'm new here but not to avocado trees.  I'm in southern Or where we do get very cold in the winter with some snow thus we built a large greenhouse 24' x 48'.  I have several trees in it avocado, lemon, orange, fig.  My avocado is a wurtz and produces pretty well but every other year.    Can anyone suggest another small avocado tree that produces every year?  I'm considering grafting a scoon from something else but haven't figured out what would be a good choice.  Any help out there??