I've used Parker Yamaha and Perry performance group for mats on my HX and my friend's GTX. The traction on these mats is far superior to the factory mats.
For the GTI/GTS/GTX models, the factory mats are secured with rivets. These need to be drilled out to remove the mats properly.
Then you need to clean and fill each hole with epoxy (DO NOT USE SILICONE or LIQUID NAILS). You might need to level off the "plugs" before laying the new mat.
The new mat is crazy easy to install. Dry fit everything just to make sure you know where everything goes. Use a pencil to mark positions like corners and edges to make sure it is centered.
Then use contact cement per the instructions (I used DAP contact cement on both boats). Let dry. And your boat will look years younger!
If you used indoor/outdoor carpet from Home Depot or similar, then it might be a lot cheaper - albeit a little unusual! No Astroturf - too slippery even though has that sushi decoration look!