Came across this, don't own a prime and unsure if there is any postage associated (someone post if there is or isn't a postage fee and I'll update thread). But thought some maybe interested.
Asus.com.au news http://www.asus.com.au/News/QbM0PtiWfxzJ0byG/
Video of GPS add on
http://www.engadget.com/2012/04/20/asus-transformer-prime-gp…
Edit: Manual found here
ftp://ftp.asus.com.tw/pub/asus/EeePAD/TF201/E7282_TF201_GPS_…
"To our valued customers:
Thank you for purchasing the ASUS Eee Pad Transformer Prime, and helping to make it the most popular Android based tablet since its launch in December 2011. We greatly appreciate feedback about our products from you, and we take this feedback very seriously. The response to the Transformer Prime generally has been overwhelmingly positive, but we understand that, in certain situations, the GPS functionality has not met some users’ expectations.
Free Dongle!
Although the Transformer Prime is not a professional GPS device, as part of our unwavering commitment to customers we are offering all Transformer Prime owners a free external GPS extension kit, called a dongle, which may help improve signal reception and optimize the user experience. We are pleased to announce this offer as part of our commitment to customer service, but it does not replace, alter or amend any existing warranties you may have. For more detailed information about this offer, please click on the link below. We also encourage you to contact your local ASUS customer support hotline directly if you are experiencing GPS related problems.
ASUS prides itself on delivering an unrivalled user experience, and we offer our sincere apologies for any inconvenience that our customers may have encountered."
I dont have a prime either but thats pretty awesome of ASUS :)