Are you looking for precovered liners or liners raw/primed to wrap?
Seems every supplier I know of has a few precovered liners.
I use Raphael's primed liners and cover them with their fabric or any other crazy fabric I find in my stash. Raphael's has a nice selection of linens and antique satins. I also use Frank's fabrics (an impressive collection of suedes and then some) and FFMI/Framing Fabrics/NEI group. FFMI has amazing selection, but be aware that they are very aggresive about discontinuing. They also have a line of silks (India) that are GORGEOUS and popular with the customers, but are very difficult to work with on liners. (The slubs keep the fabric from adhering evenly.)
All of these companies will charge for even swatch books but the first few wrapped liners will more than offset that. And fabric covered corner samples can't be beat- or maybe they can: with framed samples with wrapped mats and/or liners.
That was probably more information than you ever wanted.
Welcome to the Grumble! I just drove through your area on my way to Quetico this summer and made a mental note to get myself out on Lake Superior in a boat ASAP. Beautiful coastline!
Falcon East is another source for primed liners and fabric. They have recently added a new line of suedes and dropped their pricing on a number of items. They also have some new "free freight" policies as well as small volume (5 yards) discounting.
I went by their booth in Atlanta, and they sent me a set of 14 wrapped mat corner samples...for free.