Tman,
if i'm understanding your question right, you're wanting to know where to purchase semen & embryos?
there are companies who specialize in semen sales. they have bulls of different breeds that you can choose from. here are a couple of links. i'm sure other people can add more.
http://www.absglobal.com
http://www.bovine-elite.com/home.asp
if i remember right, you mentioned once that you weren't interested in herefords? that's really the only semen we order & we order pretty much everything through reed enterprises. they have semen and certificates on just about any hereford or polled hereford bull you could want.
we just call them & let them know what we want & they ship it ups to arrive on whatever day you want.
http://www.reedent.com/reedent/reedindex.htm
semen can also usually be purchased directly from owner(s) of whatever bull you're interested in using.
embryos can be purchased either through word of mouth private treaty or more commonly at production sales. many ranches will offer embryo lots along with their regular lots for sale.