It turns out that Moroso has a few closed loop kits (including mounting bracket) for the Elise/Exige. They mount to the transmission shift cable bracket bolts, and hence move with the engine.
The kit that the OP referenced was for the small body kit. There is also a larger body kit (43% more capacity according to Moroso) with drain valves included. The small body kits unscrew rather than having a drain valve. The large body kit is in polished aluminum only. There are two versions of the small body kit - one that is simply polished aluminum, and the other is painted black. Of course, you can paint them whatever color you want.
Here is the link at the Moroso web site:
Moroso Air-Oil Separator Lotus Kits
The individual product pages have a link to the installation instructions. It looks pretty straight forward.
Capacity: I didn't see any site that listed the capacity, but the summitracing site did give dimensions: 4.5 inches high for both bodies, 2.125 inches diameter for small body, 2.875 diameter for large body. Moroso's instructions recommend draining when half full. Assuming a 0.05 inch thick wall, that works out to 7.25 cubic inches = 4 fluid ounces. The large can is advertised at 43% more capacity, which would make it about 5.7 ounces, which is about the same as the Radium kit (6 ounces according to Radium's web site), and QWKcans (roughly estimated from external size). Saikou Michi looks to be about 7 ounces based on dimensions.
Personally, I think 4 ounces is rather small for a supercharged car, even if it is just spirited street use (no track), but, I have no direct experience to base my opinion. (Does someone else have data on caught oil for a street supercharged car that has piston rings in reasonably good condition?)
You can find lower prices at sites other than Moroso. The cheapest I found was on eBay. The cheapest (including shipping) online stores were summitracing.com and monkeywrenchracing.com. At summitracing, the small body polished aluminum kit is $267 with shipping, painted small body kit is $323, and the large body kit is $342. (BTW, summitracing incorrectly shows the painted picture for the polished aluminum kit.)
Has anyone here used these kits that could give a review?