According to Digi-Key, the Toshiba TORX177LFT-ND, has been replaced with DigiKey's p/n 1080-1432-ND, which is Everlight p/n PLR135/T9, a member of Everlight's PLR135 family. There are 2 others in the family: PLR135/T (Digi-Key 1080-1431-ND), and PLR135/T10 (Digi-Key 1080-1433-ND). From the Everlight datasheets, it looks like the /T9 and /T10 do
have flaps, and the /T does not. -- it uses a little rubber (?) plug to seal the hole when the cable is unplugged. It's altogether a better idea, so if I elect to replace the receiver altogether I'll replace it with the new Everlight /T part, whose mechanical and electronic specs seem to be compatible. The /T10 looks like it has 5 pins, not 3, so I'm disqualifying it.
I found some TORX177LFT-NDs on eBay, shipping from Hong Kong. So I ordered 2, hoping I could replace the flap with only breaking one replacement out of the 2. I've also ordered a 10' Monoprice cable to replace the Premium, Razz-ma-tazzy cable I broke the flap with, so in a couple of weeks I may have some good news. Or not. For now, the bad cable is staying in the receiver OK.
Update: Looking at the parts I've accumulated so far, I've decided it would be better to replace the whole thing rather than trying to squeeze a new flap into the old one. Then, as a bonus, I can replace it with a flapless one. So, I've ordered a couple Digi-Key 1080-1431-NDs, which have the same circuit-board layout, and appear to be otherwise identical to, the TORX177LFT-NDs I received from Hong Kong. I found the Samsung service manual (my problem child is a UN50JS7000 TV) online, and it looks like the optical jack (Samsung p/n 3707-001106) is easily accessible and doesn't require any fancy desoldering/soldering equipment. That Samsung part is orderable, but apparently not obtainable, from Best Buy.
Way more information than I thought I'd find on this, explaining why there are so many p/ns for this seemingly common part at: http://www.diyaudio.com/forums/parts...-5mm-mini.html
Thanks to all who have given advice here. While it's good to learn from your mistakes, it's a whole lot better to learn from others'