I would send them both to a small active utility sub-mixer, then output that to your single main mixer channel. It has to be active though, otherwise you’ll just be skinning the same cat a different way, with resistance issues.
Nady makes one for $25.

Art, Rolls, Samson also have some in the $50 range.
Mackie Mix-5 does the job too, though not nearly as compact as the others.