It should be possible with setTypeface() and Typeface.create():
convertView.setTypeface(Typeface.create("sans-serif-light", Typeface.NORMAL));
See Docs:
Create a typeface object given a family name, and option style
information. If null is passed for the name, then the “default” font
will be chosen. The resulting typeface object can be queried
(getStyle()) to discover what its “real” style characteristics are.
Note that excessively using Typeface.create() is bad for your memory, as stated in this comment. The suggested Hashtable is a good solution, but you have to modify it a little since you don’t create your typeface from an asset.