nine is pretty good for multiple exchange accounts. Doesn't work for OP due to lack to keyboard shortcut for delete.
http://9folders.com/purchase-license-key/
You can't buy it on Google Play. It's in app purchase.
> The license key is counted according to the device. ex) If users use the volume license key with smartphone and tablet at the same time, it will count as 2.
>You will receive the purchase email from Paypal after purchasing Nine. Please forward the email to .
>Once purchasing information is verified on our side, the license key will be delivered to you thru email.
>If you reset your license counts, the key is able to activate on the other device. If you need to transfer your key on the other device, please contact to .
> If you purchase Nine from Google Play, Nine complies with the Google Play payment policy. Google Play allows to download the paid app into multiple devices with the same Google account. Therefore, if you download Nine with the Google account which you purchased Nine before, you can use Nine without additional payment.
Where is it clearly spelled out you need to pay per device?