Would you consider a cat aged 1-2 years?
In some ways that may be better than a kitten, because you can see their personality more, and guage how they would fit in with your existing furbabe?
Just a thought 
I know nothing about Siamese apart from they are very beautiful, and can be quite vocal too 
it is a tricky one - we rescued Simba last year when he was four, which enabled the ladies at CLAWS to match him with us soooo well - he has put up with and taught so much to my 5yo daughter who used to love him a little too much but has now learned how to carry him and let him go when he warns her!
Now he will actually seek her out on the sofa and favour her almost as much as he always has done with my son!
I have this ideal of going to a rescue or a home with a litter of kittens from which we can pick one or two that we feel an affinity towards like I did with my first ever puss, Bodley . . . but yes, I realise this may not be the most sensible option, just ever so appealing.
I have read that Siamese can be escapologists - we have a huge garden, but it's not insurmountable, just that our boy chooses to know the boundaries and hasn't ever strayed beyond it. I'd quite like a savvy cat that is laid back enough not to want to broaden her horizons too much . . .
