WFCO web site has a pdf manual on that unit See Attached PDF
Model WF-8930/50 30amp and 50 amp models UL Listed Branch Circuit Breakers, rated for 120/240 Vac, maximum 20 Aac
Acceptable circuit breakers are as follows:
Cutler Hammer ........ Type Bd2020, A2020
ITE/Siemens ............ Type QP or QT
Square D ................. Type HOMT
The PDF shows 3 brands of breakers for main and Branch circuits.
Most of the standard plug-in tandem (or even single) circuit breakers you find at home improvement stores will fit the panel. They list a few to give you a choice, but they're all built to the same standard.
Salem 29RKSS Pushing a 2500 Mega-Cab CTD!
Gotta go campin!