mod_rewrite help: change the /~user/ to /user/?

Have what I thought would be an easy problem to resolve, but been struggling to find some working code.

I have a dedicated server with WHM & CPANEL 11 installed, plus a shared SSL which all of my hosting clients shared.

CURRENTLY:
For secure shows as something like https://hostname.com/~username/ which a customer can use for their site.

For unsecure of course, or reseller, it shows as http://hostname-or-reseller.com/~username/

My question is how can I successfully do a rewrite on this to remove the ~ from the URL string and still have it work properly? So these URLs...
https://hostname.com/~username/
http://hostname-or-reseller.com/~username/

Would become these now..
https://hostname.com/username/
http://hostname-or-reseller.com/username/

Any help on this is greatly appreciated.