Have the same issue on my 5 speed manual 147 2.0TS.
Saw another post talking about a nylon/plastic bush at the bottom of the gearstick that cracks and causes the gear selection to remain possible (self centring still OK), but has excessive 'play' - about 10-20mm side to side when in neutral.
loose gear stick with pics
However that was for a 6 speed (with lift up for reverse) - not the 5 speed.
I went to an establshed local Alfa specialist repairer (not dealer) and they said that the bush is not replaceable, but a whole new gear selector assembly including gearstick was required.
Cost? About A$240 for the part and another A$180 in labour to fit.
Seems a tad extreme to replace what appears to be a small, inexpensive part.
Maybe the dealers just can't be bothered fixing these, so they just supply the complete assembly instead?
Is there someone out there who can advise whether the bush alone can be replaced, or whether you need to buy the whole assembly?
BTW - the self centring issue is not what I have - I know what the fix is for that (replace the two 'top hat' plastic bushes in the selector that bolts to the top of the gearbox - an easy DIY job).