Does a metal backed sign need to be bonded to the transformer?

Currently making a sign (wood backed, steel frame, argon/mercury and krypton tubes). My 120VAC/0.9A-8kV/30mA transformer doesn’t have a grounding terminal on the backside. It does have a 3-prong plug on the primary side so the transformer is grounded. My basic understanding as a laymen electrician is that anything conductive that electricity can pass through should be bonded/grounded. Since my sign incorporates a steel frame that the gto (all through holes will have a silicone boot insulator) passes through to have all the electrical components on the backside of the sign, shouldn’t I attach a grounding conductor from the sign to the transformer? If so, how would I do that if it doesn’t have a connection for a ground?