Your agent shouldn't be irritated with you, and you should flat out tell him or her that he or she should know better! Especially if this isn't their first rodeo with a large parcel.
Put your foot down and have the sellers agent produce the survey.
Have a great day;
CEO & SR Credit & Mortgage Consultant of
Everlasting Credit Repair
Retired Mortgage Banker
If this does not work out, You may have to do your own independent survey by hiring an independent survey company.
I hope this helps !!