Modern Vespa

On my 21 mp3 500 the shopping bag holder doesn't seem to want to stay closed. Is there a spring or something to facilitate this?

My 530 does the same, there is no retaining clip or spring

That seems a retrograde step.

Are they a completely different design from the previous ones, or can you just replace them with a working one from yesteryear?

sorry i don't know, the only way to check would be to compare the parts on a parts diagram from somewhere like Easyparts

There is a screw that holds a flat metal spring deal on the outside of the bag holder under the front shield and if that screw is a little loose it will not act correctly. I ended up taking the handle bar covers, push button cover and the dash board lockup (their words) off, I didn't want to remove the entire front coachwork off to get to it. I ended up super glueing a #25 torx bit into a small 1/4" combination wrench and with a great amount of #@*!ing got tight. Now it works as it should. What an arduous task! But it works.

Page 108 of the Piaggio Spare parts catalogue shows this as numbers 17 through 21. It's actually number 21 that needs to be tight. Patients my brothers, patients.