Purchasing iMac screen and hard drive separately

No there is not. However you can buy a Mac mini which comes with an internal SSD and then use the keyboard, mouse and trackpad that you have. All you will need in addition to the MM is an external display, those start at less than $100. A new Mac mini starts at $599

Hi there!

Every iMac purchase from Apple includes the iMac itself (which includes all its components), power cord and power adapter, Magic Mouse, USB-C charge cable, and Magic Keyboard.

iMac - Apple

Hope this helps!

-Jack

you could get the iMac, and put the old mouse, trackpad and keyboard aside. it is always nice to have a spare.