Reliable being the key word. I personally had a good experience with Hotz Mats and mine arrived on time, though I have heard mixed reviews and experiences from others. Do you have a material preferences? Personally I don't mind cloth vs. vinyl unless the pieces require to be laid absolutely flat, but that's just me.
I got mine from Deep-cut studio, who does custom ones. If you're being picky with the sizes of the hexes or want a specific size mat I'd definitely recommend them.