On the 156, the gear lever gaiter is held in at the bottom by a springy frame and just clips into the console. At the top its held by a large pop-stud. Similar on the handbrake. Not sure whrther the 147 is different .. probably is knowing Alfa!
ebay ones will probably be less advanced .. the one I bought for my Pug used a cable tie to hold it to the gear knob and I had to cut small holes in the leather to fit the frame!