As I suggested in your other thread a 17-fret openback tenor is more a specialty instrument, far enough out of the mainstream that TKL and Gold Tone are the only outfits making a quality case - and the TKL is the cheaper of the two; if you're OK with a gig bag (I'm not - YMMV) one of these might work:
http://www.jdmc.com/product/C-267P.html
If you're in a large metropolitan area and/or near a good string-instrument store (or two), you might also check their bargain bins for a serviceable used/factory-second/new-old-stock case. I managed to score a brand-new Deering hardshell case ($220 MSRP) for my D-6 6-string banjo at
no cost from my semi-local Sam Ash, when I wasn't too happy with what they offered me in trade - and if they didn't do the deal with me they'd still be sitting on it in 2027; if you've got a good eye, a nose for bargains, and a talent for haggling this might be a good way to go...