Amazon.com : LifeGuard Pond Liner 25 ft. x 25 ft. 60 Mil EPDM Rubber - LG25X25-60 : Patio, Lawn & Garden
VEVOR Pond Skins 20 ft. x 25 ft. Pond Liner 45 Mil Thickness Pliable EPDM Material for Fish/Koi Ponds Water Gardens, Black CTFSMHSEPDM20SZTDV0 - The Home Depot