for that keyspan i found this in that page
" Incompatible products include:
Products which require LocalTalk/AppleTalk"
That kinda puts a damper on the keyspan
The belkin one looks the same way
Here is why:
Appletalk does not travel through USB, the OS just isn't able to do it. (although ethernet-usb adapters are available, hummm)
If you can find this product, it has been discontinued it seems,
http://www2.sunrem.com/sun01.w?pt=669783
it is a Farallon iPrint SL, note: the SL part is important. It should work, but is rather pricey.
I still think your best bet would be to ask what your local mac shop charges for a data transfer, it might just be simpler and more cost effective.