Yes, unfortunately, that is exactly how the 'system' works. You *always* have to pick an Epson paper for media type.
There is no way to insert a 3rd party paper into the driver s/w.
Are you saying that this chart isn't working for you?
http://www.canson-infinity.com/en/epson.asp#I0000bad7The Canson site does have profiles for the Epson 1400 printer so this should not be overly
problematic. You never mentioned which specific Canson paper you're using.
Once the profile is selected inside LR, when you get the printer driver dialog, select the appropriate Epson media
per the chart.
One thing that may be burning you is that Epson has had a tendency to rename their papers every now
and then (which makes users absolutely nuts!) so you may need the magic decoder ring to map the 'new' names to the
names in your printer driver.