There's a SKINS suit with 3/4 legs. I don't know of one with full legs. A quick search on Google shows these sutis are in webshops, but the prices and sizes available vary. EG,
http://www.protectionforsport.co.uk/skins_s400_compression_all_in_one. But £110 is a bit steep and it's not in my size!
I'm trying to track down SKINS S400 thermal zip top, but no luck .. :( SKINS are terrific gear: I regularly wear 'CROM' or A200 T shirt and shorts as underwear, and the A200 thermals are great as cycling baselayers :D
Good luck with your hunt!
Pete
(happy in SKINS T shirt and shorts under Asics one-piece)