They are not aero-catches. These are aero catches You're looking for boot springs. http://www.rallydesign.co.uk/index.php?cPath=74_75
I would probably mount them the other way around to that picture though - less likely to get popped open by glancing cars/barrier or ripping the pocket off expensive race overalls
get them off ebay, or JJC or rally deign. Cheap (7 iirc). Called spring clips I think. I used them on the boot of the Rado. just dont leave them undone and walk passed them, they tend to get caught on your trousers, stretch and not work again.....D'oh!