Update: Improved reliability for items with unconventionally named files, such as custom texture and material names. Removed race-filtering as this led to issues for items that can reasonably have multiple valid versions, such as earrings and hats.
A small utility that can move clothing items / accessories within a Penumbra mod folder to another item and, unlike the built-in item Swapper in Penumbra, preserve and convert all advanced mod options such as visibility toggles or model and texture variants.
The zip contains a quick guide on how to use the tool, please read it.