You can also buy some used parts and building your own package.
If I was you with the sport seats, I would buy the modules, buttons and making my own harness.
I can sell you 2 modules + seat harnesses for non-powered / passenger-powered and this guy is selling the driver-powered with memory
http://cgi.ebay.com/ebaymotors/BMW-3...#ht_500wt_1182
I saw a few times the buttons on sale on e90post and ebay.
The programming can be done by yourself by adding the option to your VO (see the programming section on e90post)
Good luck!