Said that, I'm sorry to tell you that you will need to buy one of the following, eventually: Sata cable (in case you have a desk computer or by somehow your iMac has another Sata slot)/External HDD-SSD/Pendrive
I'm an experienced technician, and I can help you with this for some money. In case you're interested, chat me on Skype (click on the image at my signature to add me) and include this:
-How old is your HDD? Had it made any 'clock' sound when you turned your iMac on? What had you been doing when it stopped working? Was there any energy shutdown recently? Have you got a desk PC?
-Open up the back of the iMac and take some photos for me (specially in the place for the HDD).
Once we sort the things above I'd be able to give an approximate price for this