Did you search for the keywords "HDP replacement parts"? Because that isn't the way to do it. First you open it up, figure out what's broken, which in cases of things getting "fried" would usually have really obvious visual clues, and look up the parts numbers on those. If it's a microchip it's etched on the top; if it's a capacitor, it'll be printed all over; sometimes regulators not only have the parts number on them but also printed on one side of the board next to their mount (I assume the redundancy is because of their higher likelihood to get fried than all other components). You need to send NuForce an email and ask for a schematic diagram, which any tech will find useful when he takes a look at it.
You also won't need to be the one to repair them yourself, you just need to find a reliable and trustworthy enough tech. I was lucky enough with that when my Meier Cantate.2 broke last year. I emailed Dr. Meier in case he might have some advice on how to service it, as well as schematic diagrams (which I knew a repair tech would need), then brought it to a local Shanling distributor (mass manufacturing is subcontracted to Shanling) before I ordered parts, in case I missed anything apart from the fuse, one regulator (I didn't know what it was before I Googled the parts number, but the top part obviously looked fried) and the power supply. Turned out another regulator was also fried, and then when I searched for the power supply model, I can find it on the manufacturer's website but not on parts retailers like DigiKey and the manufacturer wasn't responding to my emails. I sent Dr. Meier another email asking if he can approve another PSU I found on the web, and he sent me a link to another model that had nearly every spec identical to the original (and most importantly, 110v to 240v operation). Ordered the parts, brought them over to the distributor, and they brought my amp (still in the box) out of their storage locker. After replacing the parts the tech also did extensive testing (the tech used it for hours as long as nobody needed to talk to him) and detected crackling sounds on the left channel but only with the analog input; he cleaned and up and fixed the soldering. When I picked it up the tech dropped a hint on buying it from me after he heard it with my HD600 (fat chance, I love this amp enough to spend $70 on parts and shipping, plus $25 on service fees).
In your case you'll probably have to ship the HDP to someone who can fix it, if not NuForce then anybody else who might take on such a job (again, have the schematics diagram handy). If I was in the US though I'd look for a local hi-fi retailer,* drop by and check if they have a tech around or if the owner has a side business of servicing other parts (those dealing with vintage equipment usually do - heavier stuff are better repaired locally because of shipping costs). Check for example speaker forums and ask if they know such a store in your area code and surrounding areas. If there's none within 25 miles or so, check if the local community college has a program for training techs (if not a full-blown electrical engineering program), look for a student or even an instructor who can help you out, and bribe them with beer and pizza (or something). Tell them it's out of production but you really like it for the performance and form factor (small size, PSU the size of a netbook's, easy to pack, etc).
*A few years ago my brother in CA wanted a Grado but didn't want to get it online. I checked Grado's website, found one in his area, and turned out it was smack behind his college campus. Turned out they also sell Musical Fidelity and other brands. AFAIK, they can also coordinate with manufacturers and distributors on behalf of customers (this was the practice before internet sales and service tickets, obviously). Also saw a shop that was kind of like it on Storage Wars - small unassuming place, not necessarily in the same kind of place where you'd think Gucci and B&O showrooms would be - but specialized in vintage gear. To put it in perspective, Fast and Furious car parts dealers sell expensive stuff but they aren't in areas like that either, but you have to check area codes with a tendency for higher prices for homes - the one I found for my brother was in such an area (yeah, I'm half a world away and I can profile his surrounding area based on similar patterns where I am).
