I usually can find that type of trim vinyl (really light weight thin stuff and does not wear really well) in specialty trim or upholstery shops. In order to get the correct horizontal and vertical seams you really need a sonic welder/seam roller . we have ours made from heavier vinyl and sent to a place in california and have a roll of 40 yards done at a time. You could try a vacuforming company since they usually have a sonic welder and might do it cheaper for small quantities.
