[mothered]

I could call them back and make an excuse to send the new one first.

You can do this by saying that you've left the keyboard at your brother's house and due to new restrictions of the COVID-19 situation, you cannot visit him, hence It will need to be posted to you.

Tell them that you urgently need the new keyboard and the moment your old one Is received, you'll send It. It's just one way of manipulating them to first dispatch the new one.

Or I can box them.

What's the weight & dimensions?