Hi Jeremy,
Looking at your site, I would probably position the wrapper element to a fixed position first with this custom CSS:
[html]div.et_search_outer {
overflow: hidden;
position: fixed;
width: 400px;
right: 7px;
top: 100px;
}[/html]
Then change the width of the search to fill this element:
[html].asp_main_container {
width: 100% !important;
}[/html]
This should be a good starting point 🙂