You're kind of confusing two separate things.
A security check lap top bag doesn't really mean anything, in Dublin certainly they ask you to take the laptop out separately anyway so you don't need to bother having a bag for the laptop itself.
Ryanair require you to have all your stuff in one bag, if your laptop bag/case can fit into your normal suitcase then fine, if it can't you won't get it on board.
Would a "sleeve" like this do?
http://www.amazon.co.uk/Targus-Luxury-Neoprene-Enhanced-Protection/dp/B009HQNK2S/ref=sr_1_2?s=computers&ie=UTF8&qid=1368018465&sr=1-2&keywords=laptop+sleeve
Do you really need a separate bag/case for the laptop, will it not just fit into your suitcase?