Hello Wouter,
to download them, all you need to do is go to the "My downloads" section of your account:
http://www.joomlathat.com/account/downloads
There, next to the download button of the component you will see a small down arrow that if you click on it, it will open a dropdown showing the available joomla versions.

By clicking on the Joomla 3 option, it will only show you the files you require.

Please, tell me if this solved your problem.

Hello again,

Sorry, I just realized that your subscription is for Joomla 2.5 only, that's why you can't download the files for Joomla 3.x.
To have access to the Joomla 3.x files, you need to upgrade your subscription plan to the "combined" one, which includes files for all versions.
You can upload just by paying the difference, you don't need to buy a whole new subscription.

if you're interested in upgrading, please let me know and I'll prepare the invoice for you.

All the best,
Joan

hi Joan,

Yes please, I'm interested. Please send me the invoice for the difference so I can use the Joomla 3.xx files.

regards,
Wouter

No problem, you can find the invoice here: http://www.joomlathat.com/index.php?option=com_invoices&view=invoice&id=23088

I have paid the invoice. Please let me know when the download is possible!

Thanx