The WFCO converters are a known weak point. I'd advise against replacing it with the same.
That said, I bought an Iota charger, which fit nicely in the existing WFCO housing. I simply pulled the guts out of the WFCO, dropped in the Iota.
It works flawlessly. There's no high pitched squeal, like with the WFCO converter. The lights also stay at a constant intensity, despite the loads.
I bought my Iota charger from an eBay dealer. I'm also using a 75A Iota with my solar setup at home. FWIW, these can be used with, or without a battery. Very clean power supply.