Probably out of luck. Microsoft stopped selling XP about a year ago I think. So you can try your luck on ebay, but odds are you're just going to get scammed.
Still, I fail to see why an OEM copy of XP wouldn't work here. I think you might be misinterpreting HP's advice, and they're saying you need to buy a copy of XP through retail outlets, not necessarily a retail copy of XP.
I am trying to find a RETAIL Windows XP program to purchase. I was instructed by HP that is what I was going to need to be able to boot my hp753n since the recovery D: file was accidently deleted and that the HP Recovery Disc is not working (2002). Can anyone help me with this or tell me who to contact to get one? Tired of looking.