Here in the US, I have found Chicago Canvas to be the best vendor. I bought the brown canvas I used on the re-do of a Dingo roof by the meter.
They sell either yardage to "Sew your own" or prefinished tarps.
Here is a link to what I would get for my carrier.
http://www.chicagocanvas.com/product...as-tarpaulins/
Price for a 12 x 16 finished tarp is 117.15 plus shipping.
16 OZ FLAME RETARDANT CANVAS TARPAULINS
$21.35–$548.95
Strong, breathable, water, mildew & flame resistant canvas
Triple thick hems, Grommets approx. every 2′ on all sides
Additional sizes available – Contact us for a quote
Sizes listed are CUT SIZE, tarps will finish smaller after sewing
SIZE Clear
$117.15
USe this link, then poke around to see the available colours.
For our use, they have natural, Medium green, OD green, Dog Shit Brown, and the yellowish "gold" colour we find most of the repro British style tents being made from.
Good source for serious hobbyist sewers and professional sailmakers - Sailrite.
http://www.sailrite.com/#
They have commercial level compact sewing machines (like you would keep on your sail boat) as well as the ones with tables and under table motors.
They have loads of too modern stuff, but they have brass grommets and a good reference for thread and needle size and usage. Also Lift-the_Dot snaps and tools and lots of hand sewing tools like palms and needles.