I've lost the power cord for my HP DeskJet 712C printer. How should I
go about finding a replacement?

Your best option might be to contact HP directly at the following
phone numbers:
general inquiries    800-752-0900  
general sales inquiries 800-752-0900  

To order directly from HP click on the following link:
http://h61003.www6.hp.com/
If you are in the US, click order parts in the U.S.
Next, click on Find Part Number to the right of the screen.
Where it says "select your country or region" click on United States.
Where it says "enter an HP Product number or name" type in Deskjet
712c and hit enter.
Now you should look on your printer to see the exact model number you
have click on the corresponding model number on the website. The three
possibilities are "C5894A, C5894AR, C5894B".
After you click on a model number, change the Keyword to "Power Cord".
Type in the Quantity and click on Order.
Click on next.

This page shows the power cord listing as costing $14.00 (without
shipping and handling):
http://partsurfer.hp.com/cgi-bin/spi/main?sel_flg=partlist&model=C5894A%2FB&HP_model=&modname=DeskJet+710C%2F712C&template=secondary&plist_sval=Power+Cord&plist_styp=subcat&dealer_id=&keysel=Power+Cord&catsel=%3F&ptypsel=%3F&strsrch=&pictype=I&picture=%3F&uniqpic=

If you need any clarifications, please let me know and I will do my
best to further assist you.

tisme-ga

Go here:
http://search.gateway.com/search/GAS_searchResults.asp?gasp=3&txtKeywords=printer+power+cord&cboSearchType=keyword

At the bottom left you'll see:

Supplies
Cable Locator
Ink Locator
Office Supplies
Kingston Memory Configurator
SimpleTech Upgrade Navigator


Select CABLE LOCATOR. A neat little window pops up that lets you
select the type by looking at ports that look like yours.

If that doesn't help, try this one:
http://teengirlsgonebad.com/search.asp?keyword=Ac%20Power%20Cords

It may halp you identify your cord so you can shop for it locally at
OFFICE DEPOT or RADIOSHACK etc.

Regards;
tutuzdad-ga