Yep, expired. Digital to analog tv converter, dtv converter, etc. I use just tv converter on Craigslist and filter through the results since most of the idiots there don't use the proper terminology and CL uses a bare-bones search feature; also have to look through those results that list a TV as they tend to batch them together (TV is nearly worthless but if not a heavy one might be a good deal and can donate the TV).
A year ago I was lucky to receive a 34" HD widescreen CRT so I started watching CL for HD tuners (hd tuner and hd receiver). Needle in a haystack it was but I found one for $20; old but it worked fine for me as I have an attic antenna. Now more recently I stumbled across a Hughes DirecTV receiver for $20 when I went to buy a DVD recorder; he was showing me other stuff, it was almost new and in the box, I was skeptical it would work but the manual claimed it would so I nabbed it up.
Summary of what I've learned:
There's old HD boxes like the one I got (Motorola) but since they have early generation tuners they may not work so well in weak signal environments.
There's satellite boxes, and maybe cable boxes, that have ATSC tuners but you'll have to figure out which ones will work without a subscription. I know DirecTV made them require a subscription after a certain point in time so it has to be the earlier models. Now mine does have a 4th gen tuner which is good. There may even be some that have DVRs that'll record manually (i.e. cannot use the guide/Tivo-like record feature). Anyhow I see a lot of sat and cable boxes on the cheap but don't know what's what - there may be threads on AVS and elsewhere that list them out if you have the time to search (I stumbled across a HD DVR thread on the subject here once).
Now I would think that the CECBs have the latest gen tuners, not that all brands are great. I say that because if I'm correct about the previous pgh then CECBs came out after the sat and cable co's started requiring a subscription (my Hughes box is 2003). On the other hand those HD boxes are probably more sophisticated otherwise as they were much more expensive and feature-rich ($500+). Then there's the aspect ratio - I would think the HD boxes would have a setting for 4:3 but I can't guarantee it.
I think there's still a few CECBs being sold new, just search the 'net. I just saw Amazon still has Zinwell but it doesn't look anything like mine and appears to have been stripped of some nice features (probably outsourced and cost-reduced).
Of course there's a plethora of all kinds of stuff on eBay, mostly used I suspect. Some folks saved some of the CECBs and sell as new in box, which most probably are, but the warranty is long gone and they've never been burned in (I rotated all of my backup units through their warranty period to weed out any infant mortality failures). I just don't mess with eBay that much for this stuff because I think I can find better deals on CL due to locality (plus no S&H) and folks on CL aren't experts at pricing stuff.
Edit: Forgot to mention there's those boxes that include HD DVRs like the ChannelMaster CM7000PAL (formerly a Dish network product). They're new like $300 or so but I just spotted a tempting one they say is like new for $125. There's also DVD recorders with built-in ATSC tuners.