I've seen Marathon I, II, and III seed for sale at Armstrong Garden Centers and also at Ewing Irrigation.

http://armstronggarden.com/store_locator/

http://www.ewing1.com/general/ews_loc_california.htm

for Tall Fescue I think the spreading rate is usually around 8 lbs. per 1000 sq ft.

Its pretty expensive. If I remember the prices right, a 5 lb. bucket of Marathon I is $25, and a 5 lb. bucket of Marathon II or III costs $30. But since you only have 400 sq. ft. you'll only need one bucket.

yes, I realize Marathon can be expensive but heard that it maybe worth it in the long run.
or does anyone have any other suggestions for cheaper seed?