I have a thread on here somewher about the mat sizes & fitting etc, sure if you search for it..
In a nutshell, the fitting you have are useless (I had them in my car also) unless you have the actual factory fitted mat option (which most dealers wouldn't order it seems) A very small number of cars turn up from Italy with them fitted (still same with newer models, Mito, Giuliette etc apparently)
Aftermarket ones with that fitting it seems are only available in LHD from places such as Alfisti and are shown in the 159 accessories brochure, again as LHD option only.
Best advice is to find a good quality set (some as mentioned on ebay) or take the hit and get a set from a dealer.
Here you have 2 options, the really heavy duty 'luxury' ones (about £70) which are actually a dark grey colour, or the cheaper (about £50) black ones.
I resorted to removing the little pin type fixings and using the bigger ones from ebay, now have properly fitting mats front & rear.