I have that same laptop and have bought a couple of power supplies for it. The last one I bought was through ebay last September - same seller has them listed for £6.25 including the mains lead and P&P - http://www.ebay.co.uk/itm/19V-3-15A-AC-Adapter-charger-for-Samsung-NP-R510-NP-R60Y-R50-V02-GT8000-NP...
It's been reliable - doesn't get hot or buzz and the lead between the PSU and laptop is a good length. The plug seems well made and and I've had no problems with it despite making heavy use of it for several hours a day. Delivery was also very quick - two days from paying to arriving.
The seller has a very good rating 99.8% off ~8,000 sales in the last year.
I'm always wary of recommending sellers because nothing's perfect and I'd hate to get the blame for something going wrong but I will say that I have that seller bookmarked and would use them again. Obviously, check the latest feedback before using any ebay seller as there are sometimes high rated sellers who start getting a lot of negatives just before they go bust.
If you're wary of ebay, it's worth noting that many of the sellers on Amazon are exactly the same large sellers as on ebay so you can often look at the feedback on Amazon for more detailed information from buyer then buy through whichever has the best price.
