I am also looking for suppliers of parallel output (DB-25) interfaces. I use the word interface because it is specifically designed for use with CNC interpeter programs and has terminals for the power supply voltages, step and direction, and home and limit switches.
So far, I have found 1 manufacturer (which is in Canada). The name of the company is Axxus Technologies. I contacted them this week, and they will not have any more boards for at least 4 or more weeks. The US price for the interface board is $60.00.
Sorry, I don't have their e-mail address at this point in time. However, there is a thread on this site "Axxus" which does have their e-mail link.
If you get a list of suppliers -- PLEASE POST SAME.