Mathew Wagner,
Terminal Units turn up on eBay now and then for reasonable prices.
There is an MFJ-1224 auction ending Sunday.
Download the book at the link he provides and save it to your hard drive.
Look at the book if and see if you might like the TU.
I have a 1224.
It has one unusual feature, The loop connects to an RCA jack.
I put a red label by my loop jack and colored the RCA plug with red magic
marker. That's called idiot-proofing.Otherwise I might forget and plug the
loop into the wrong jack with disastrous results.
It will stand alone (Does not actually need a computer connected to it.)
connect a loop supply and Teletype to it and you will be printing.
I would not use a loop supply greater than 120VDC. I built one with
a 57 volt transformer that gives me 80VDC at 60 mils so I don't
over-stress the keying transistor.
His shipping is less than ten dollars. I would snipe it at maybe $70 and
hope to get it for less.
Or, every couple days do an eBay search for "rtty". Then put it in
order of lowest price+shipping. That will turn up most terminal units.
That is what I do.
Not all TU's have a loop output. That is the first thing I look for.
TOM N3CRK