Hardy pollinizer for buerre giffard pear?

Some years my buerre giffard blooms well in advance of any of my other pears
It’s happening again this year. Which Has me looking for a pollinizer to graft in for the future. Needs to be z4 hardy
I think I have read that summercrisp blooms about the same time…but I’ve also read that summercrisp blooms with patten and Parker…both of which I have and usually bloom later for me, just as the buerre giffard is winding down.
Any suggestions for a hardy early blooming pear? Doesn’t need to be particularly good, just a viable pollen donor

Perhaps the species pyrus Ursinensis - Harbin pear . It was used in the breeding of Patten and Parker I believe . Does yours bloom with or after flowering pears ? I know this is nearly a year old post but just noticed it .