Well... that depends. What's it worth to ya? Boat manufacturers make proprietary arrangements with Vinyl Upholstery makers. That means that the vinyls used by OEM boat builders are not strictly available on the open market. THAT SAID, sometimes you can come close.
If the boat is less than 5 years old, then the boat builder might have stock in your exact vinyl. If the boat is older or if they do not hold any more stock that is an exact match, There are two more options. Boat makers sell their roll ends to dealers that handle only "close-outs" and "over-runs". (You might even find a replacement dashboard part for the one that's cracked, while you're at it.)
Not only roll-goods but also OEM Captain's chairs can sometimes be found. I recently found a brand new Captain's chair for a Chaparral. It was about $895. That is about what we would charge, because the chair was complicated and we don't have their pattern as a starting point... BUT, we were able to just install the new seat and move on to our next custom project; no real savings in money but it put us 2 or 3 days ahead on the next project.
The second option if the boat manufacturer cannot help you is tricky. Marine Upholstery Vinyls have three main characteristics that people mean, when they ask, "Can you match my boat's upholstery vinyl?" or "Can we get an exact match for my boat seats?" Those three characteristics are COLOR, GRAIN and SHEEN. Color is self-evident. Grain is pretty obvious too. Grain is the "skin texture" of the vinyl you want for your boat. Sheen is less obvious to most people shopping for Marine Grade Upholstery Vinyl to match their boat. This has to do with whether the coated fabric maker made the surface "matte" or left it with a high-gloss finish. Of course there there are infinite vinyl sheens, colors, and grains made for boat interiors, and there are other subtle factors. Shoppers don't generally think of the surface thickness of the original vinyl. (30oz is typical for marine vinyl) If the original vinyl had a 1/4" foam layer on the back, that can be added by your upholsterer. If you find the right pattern without FB on the SKU number, you have solved your problem.
There is, however, another way to go... Sometimes the boat owner can find an online partslist for the make, model and year of their particular boat. That list might tell the vinyl manufacturer and even the color and/or pattern of the vinyl that was used on the boat originally. THIS WILL STILL BE A PROPRIETARY VINYL, However, it greatly narrows down the job if you can know who made the vinyl. They might have taken a shortcut and you might find the right color and sheen... even though the grain is smoother or bumpier. That might be close enough if you're reasonable.
The probable choices are narrowed down when you can find the vinyl maker's name because sometimes the vinyl coated upholstery industries make things a little easier on themselves. Sometimes Spradling, Nautalex, Morbern, Nassimi, or Naugahyde seem to use an existing "stock" color with a different grain or give a different sheen to make the run unique. SOMETIMES, two out of three ain't bad and we can help you quickly. So don't be sad! (you remember the song) These are the experiences when an upholstery shop tries to find an exact match for your boat by just sorting through all of their samples.
That said, if the boatowner is a real stickler for an exact match, these minor difference can be enough to put some people off. That drove one boatowner we recently did work for to spend 15 hours searching until he found the exact match he wanted. This writer has personally spent 4 hours on just "searching". At $75.00 per hour, that's $300 spent while we found a match, there is no guarantee.
All that said, HERE is the number one reason NOT to spend even one hour trying match your exact upholstery vinyl of a boat seat: The only reason for finding an exact match is because you only intend to do SOME of the upholstered parts at this time. Guess what? the same vinyl might no longer be available when the other upholstered parts wear out, too. SO the long hard search only serves to wax you into the corner when the rest of the seat or back parts need to be recovered!
CLC&U recommends that you spend very little time on what can prove to be a fruitless search. A close match is usually the best choice, once you consider what you are really asking when you say, " Can you find an exact upholstery vinyl to match the rest of my boat?"