Siamese Cat Clip Art
Siamese by ~Mathas on deviantART
There are one or two websites that are the best for Siamese cat clip art. It depends whether you are prepared to pay a bit for it. There are sites where you can get free Siamese cat clipart but it will be relatively poor in quality.
The best site for Siamese cat clipart must be istockphoto®. This is the premier supplier of photos and clipart for purchase and use under license. As it happens, having just now done a search on istockphoto® for Siamese cat clip art there are only eleven images. You will need 15 credits at about £1.10 per credit in the UK. As you can see it is not cheap but neither is it expensive if you set high standards. You will need to check their terms and conditions. This is important.
This page on squidoo has some reasonable images.
Check out deviantART's siamese cat page. There is some nice Siamese cat clip art but please check the rules before using these image. The images are not strictly speaking clip art but close.