Rich, any RV parts or service center should be able to get you the gasket you need; give them the piece you found on the ground so they can match it. Not seeing what type of gasket you need is hard to say how it will attach. They should be able to instruct you as to how to install as well. Good luck and keep us posted.
I have just found that we have two threads going for the same topic so I am going to lock this one. Please use the other for replies.
Mike, RVIA & RVSA Certified Master RV Technician
Amy, Dr. Assistant - Roxie & Mei Ling, four legs each
2000 Gulf Stream Scenic Cruiser 450 hp & 1330# torque
06 Saturn Vue, 06 Chevy Z71 4x4 & 2014 Corvette Z51 M7