I have looked everywhere for the past 3 days, which no such luck.
Can someone tell me how to make your own custom collars/accessories?

No one can help?

You expect an answer after an hour? We don't spend our every waking moment lurking here waiting for questions.

As I said in pm, start by cloning a similar item with TSRW or s3oc, export the mesh and textures, and modify them. Any tutorial on making clothing or accessories for human sims should get you started on how to do the meshing and texturing. Then replace the meshes and textures in your cloned package and test. Post back here with specific questions or problems.

Here are the MTS set of tutorials on CAS parts. Note that you won't be able to use CTU with pet stuff.

http://www.modthesims.info/wiki.php...3_CAS_Tutorials

Yeah I am having the same difficulties. I REALLY wanna know how to make my own saddles for the sims3 horses. But I just can't find out how to clone the files and import them into a 3D program for re-modelling (If that is what it's called). I am such an idiot with this! xD Anyone know where to find a "pet's accesory meshing for dummies"? :P

Or just wanna be able to f.eks. to move lakeside saddlerys allround saddle further down on the horses back. I really wanna use that saddle in the game but it looks stupid when the saddle is in the wrong place for the sim riding the horse ^^''

Have you tried my suggestions above, to clone with TSRW or s3oc, export the meshes, and use Milkshape to modify them? As far as I know saddles work the same as any other clothing/accessory and you can use the many tutorials on CAS parts as a guide.