As mr_nobody mentioned Vox doesn't have access to the Android Market but luckily both apps you mentioned are available elsewhere.
Aldiko Be sure to use the email link on your right and in the message after you press Grab It (you don't need to use a real email as it always shows an error message) press the HERE word for direct download of the app.
For Opera use the direct URL of
http://m.opera.com/ for quick easy install direct from your Vox.