As a former kitchen designer (for 20 years), I have some experience with solid surface countertops. Maromeo is correct; they are considerably heavier than laminate (Formica) countertops. So not only do they require special support, they will subtract from your available payload capacity. They are typically sold
only as 'installed" products, and the installers must be certified by the material fabricator. They will be priced at 2 - 3 times the price of installed laminate products.
Most solid surface countertops are either stone-based (granite/quartz), glass based, or acrylic/acrylic blends. The stone/glass based ones are much heavier than acrylic and are more rigid. The added weight and the rigidity of the stone/glass tops make them unacceptable for use in an RV, with the constant bumps, etc. Acrylic is a rather soft, flexible plastic that does lend itself to use in RV's, as wags999 recommends. They are durable, stain
resistant, and will last for 30 years or longer. As mentioned earlier, acrylic is rather soft, so it will scratch and you should
never cut on it or drag rough items across it. However, minor scratches can be buffed out with a Scotch-brite scrubber pad. Normal cleaning and wiping of the surface tends to "polish" it, so over time you will see "shiny" spots where it is cleaned most often. Those can also be buffed out with an all-over buffing with the Scotch-brite pad. Shiny, polished finishes are available on some colors/patterns, but scratches will be much more visible, so they aren't generally used on a kitchen countertop. Several brands are available. Jayco switched from Coreon to Himac several years ago (probably for cost savings). Due to special installation concerns and marketing restrictions, Jayco
will not sell you a replacement top for your island.
Sometimes, a certified fabricator will have a "remnant" they may be willing to sell you for DIY use as a cutting board or table top. But as a countertop (especially if there is a sink or sink cut-out involved; probably not. As for sink options: Integrated sinks (solid surface sinks rigidly glued to the underside of the countertop with the seam buffed to be virtually invisible) are not an option in an RV, due to the bumping and twisting in an RV traveling down the road. Most RV's use specialized stainless steel sinks that are glued to underside of the countertop. The lighter weight of the stainless steel sink and the flexibility of the silicone glued seam make a good choice for RV's. Finally, a sink may be dropped into a sink hole from above the countertop. That is what is typically used on laminate countertops. The seam is made water tight by sealing it with acrylic/silicone caulk, plumber's putty, or butyl caulk.
Because of volume discounts, Home Depot or Lowes are excellent places to go for residential solid surface tops. However, they will not allow their fabricators to install in an RV. Some stores won't even do an installation in a mobile home. Therefore, your best bet is probably a local fabricator. If you make a simple, two-dimensional sketch of your countertops (looking down from above) - including the measurements along the back side (longest length on the island), and the depth from front to back - a local fabricator can give you a fairly accurate price estimate. They will have to schedule an on site measurement before they can give you a finished price and start actual fabrication.
Sorry for the lengthy post,
but hope it helps with your decision.