Loose fitting power cord.

You could also use an IEC C13 to C14 adapter...

Thanks everyone so much for your suggestions!

The electrical tape might work, but sounds to me like a perfect excuse to put on the dark, dark goggles and pull out the welding equipment.

The only helpful suggestion here was from mc.  The teflon tape belongs around the brass contacts of the IEC so that it electrically, not mechanically, has a tighter grip.

Wrap the Teflon plumber’s tape around the termination of the PC. This will make it fatter and will be a tighter fit. I have used this method many times.
If the cable is extremely heavy, I use a block of wood or heavy sponge rubber underneath the cable behind the component.

Electrical tape is the first method I tried and it’s a bitch to clean it all off. No adhesive on Teflon tape and it's resistant to heat.