Not a full solution, but once upon a time I had a Sandisk Sansa e280 that I jailbroke with Rockbox, and it appears to have manual bookmarking https://download.

Not a full solution, but once upon a time I had a Sandisk Sansa e280 that I jailbroke with Rockbox, and it appears to have manual bookmarking https://download.rockbox.org/daily/manual/rockbox-sansae200v2/rockbox-buildch5.html#x7-830005.3 https://download.rockbox.org/daily/manual/rockbox-sansae200v... "Note: Bookmarking only works when tracks are launched from the file browser, and does not currently work for tracks launched via the database. In addition, they do not currently work with dynamic playlists." https://www.rockbox.org/ https://www.rockbox.org/ https://www.ebay.com/itm/SanDisk-Sansa-e280-8-GB-Black-MP3-Digital-Media-Player-Working/324362830048?epid=82738875&hash=item4b858800e0:g:348AAOSwloxfouCR https://www.ebay.com/itm/SanDisk-Sansa-e280-8-GB-Black-MP3-D... As I recall I could also add a SD card to this model, but I don't know what its max size is.