10-10-2009, 02:06 AM
They're called pressure balance faucets. I did a super quick Google search, and this Delta unit showed up at Amazon. I have one for the combination tub/shower and there's one for showers only. Since mine are about 15 years old, they look a little different than the one in the link but they work the same.
http://www.amazon.com/dp/B000FE0RX6/ref=...PDKIKX0DER&tag=googlecom09c9-20&linkCode=asn&creative
http://www.amazon.com/dp/B000FE0RX6/ref=...PDKIKX0DER&tag=googlecom09c9-20&linkCode=asn&creative