I don't know where you can find them, but the tilesets are quite easy to rip with Temporal Flux. To do it you'll need a good image editing software, like Photoshop or Paint Shop Pro (this is the one i use).
First open Temporal flux, choose the location from which has the tileset you want, make sure that the L12 tiles window is totally seen, and take a screenshot.
Now paste the image and select and copy the tiles.
[img=http://img185.imageshack.us/img185/182/2stuo6.th.png]http://Paste the tiles as a new image. It should look like this.
Now resize the image to 200%. Make sure that you use pixel resize to change the size of the image, otherwise the tileset will lose resolution.
[img=http://img180.imageshack.us/img180/474/4stbv8.th.png]Now create a new image of 256x???? (the ???? represent any number, but generally it has to be higher than 2000).
[img=http://img182.imageshack.us/img182/1315/5stjf0.th.png]Now paste the resized image into the new image, don't change the size of the tiles, if they don't fit, just paste the ones that were out of the image, below the others. Now make all the color that should be transparent, transparent, paint shop pro has a background eraser tool that can help a lot here. Finnally the image should look like this
[img=http://img82.imageshack.us/img82/5989/6stxq9.th.png]Finnally save the image to the tileset folder of RPG maker Xp and you should have a nice chrono trigger tileset.