When my Lambert failed I replaced it with an Echo Charge by Xantrex.
The specs seemed to be so similar.
The item is: Xantrex 82-0123-01 Echo Charge for 12 and 24V Systems from Amazon for about $100.
It was a simple swap and my chassis battery voltage now shows that Echo it is doing the job.
(On my rig, house and chassis battery banks are monitored 24/7 by LED voltmeters.)