Some TeX packages benefit from the acquisition of specific fonts for best results. For example,
mathdesign lacks small caps for Bitstream Charter, but supports an "expert" option that makes use of Windows Postscript version of these, that requires ownership of the relevant font. These formats are, however, generally available as parts of expensive comprehensive bundles.
Are there resources for TeX users that provide a way to purchase the specific font features "missing" from popular TeX packages, without having to purchase expensive bundles?