I found some more DEC MMJ crimpers that look pretty decent out there on eBay, but
they're not well labelled.
https://www.ebay.com/itm/Ideal-30-558-Crimp-Die-for-RJ-11-MJ-Modular-Plug-C…
$15 plus shipping new (2 avail) MMJ die for ideal crimp frame 30-506.
There are new and used Ideal 30-506 frames on eBay for reasonable prices. Search for
"Ideal 30-506".
https://www.ebay.com/itm/Ideal-Twisted-Pair-Kit-33-650-w-Plugs-and-30-506-3…
$55 plus shipping used kit (2 avail) including above die, other dies, and 30-506 crimp
frame plus cable cutter and stripper.
https://www.ebay.com/itm/IDEAL-TWISTED-PAIR-KIT-45-074/301901645725 $55 free ship in US
used Ideal kit (without case) similar to above including DEC MMJ and other dies and tools,
but of a different vintage
And it could be worth searching for Crimpmaster instead of Ideal. There are lots of used
Ideal Crimpmaster frames with dies, but not all of them include Ideal in the description.
Maybe some of them are DEC RJ-11 MMJ.
-- Ron Pool