Not exactly the same but, have you considered a ProLite pad?
Comes with changeable foam pieces so you can mix and match the amount of padding.
http://www.prolitepads.co...reliefpads/reliefpads.htm


Nuumed make the hiwither products, their page is here
http://www.numnahs.co.uk/products_numahs1.html
That's all the half pads

Griffin also mae a hiwither range
http://www.tackandski.co.uk/prodpage.asp?ProdID=856
That's an english site but they probably ship, or you can find them in the US I'd assume.
http://www.tackandski.co.uk/griffinnumnahs.asp