NEC AD-7543 has the same specs as NEC ND-7551. Probably AD-7543 is the new version of 7551?
You can find it at this UK online shop
Navigate to product search in the page left menu, type in 7543, do the search and after retrieval, click on returned "DVD+/-RW Drives (1)" . Currently the item is sold out, but you can phone them, or give your email address to alert you, when the drive arrives (I've done so already).
You can also check the specs here - (it says drive is comming soon- but the price is little bit higher than in the wstore)
I did check the size of it and the connection type (50 pin IDE), so I hope it will fit into my Prestigio 157 - wanna ged rid of currently installed QSI SDW-082 (which is really pain in the *ss)