I now use a surface pro 4 for running siemens NX and cam for programming hence me seling my HP zbook the thing is easily as capable, though its not going to be doing FEA or rendering so if thats your bag ….not maybe the best tool (and the battery is only 4 hours when being used in superabusive mode)
to answer your question however
Dell outlet
ITC sales
and a seller called XPN1 on ebay often gets dell precision laptops for cheap money (i got a 24 core t7910 workstation off the guy for 1500 quid ) a m5510 i7 was 1200 quid ive seen them on his shop for 799
**personally wouldnt touch laptops direct , once they have your money you are f****D if anything goes wrong