Pink eye wouldn't so much come from the surround (though it will get sweaty and gross), but more from your eyes/lashes touching the lenses (especially when your demo person does the adjustment and gets too close before backing it off to a comfortable level).
The easiest fix is to take your own hand wipes and insist on cleaning the inside and drying the lenses before putting it on. It won't solve the gross surround if they aren't switching those out every time, but use a hand wipe on your face, wiping away from the eyes, when you're done.....and most of the transmission risk is gone.
Before commercially available VR huggies were a thing:
https://vrcover.com/
I used to use long black dress socks (new) to make my own.....not that you would do this to go to a demo.
Cut in half long ways with fabric adhesive strips and weak rubber bands (folded into the edges and glued to form elastic bands on the outside)....they worked pretty well. I used a long zip tie to give form to the inside stretch around the eyes (again folded into the seam) as well.