I listen to a ton of audiobooks as well since I have over an hour each way on my commute. I have the opposite problem though since I get my audiobooks from audible.com and it's not convenient to burn a bunch of CDRs to listen to each section of the book. The cleanest solution in my case is get an iPod interface and listen through that.

To answer your question, the only cassette players I've seen that might work in the FEH were on Ebay.

My 4WD
Wife's 4WD