OK... A little funny story, told on me, that may help you make a fix on your Lavalamp.
Early last summer, like our buddy MikedaBike, I had some ceramic tile work to do in the master bath which also included removing a bathtub -as in hole thru the wall type- removing.
New tub needed the 2x4 ledgers altered and a bunch of other plumbing details. Had it all about done and ready for the new tub. Just a couple more nails from the pneumatic framing nailer...
Set the tub and secured it. Did a massive amount of ceramic tiling and general wrap-up work. It's boo-ti-ful sez my bride.
That afternoon, the washing machine is going at max rpm and wife tells me, "There's water on the bathroom floor."
Long story short, one nail set itself about 1/16-inch into the washing machine drain line... just on the other side of the bathroom wall. YeeGads!
Fortunately, the plumbing inspection panel in the laundry room allowed me to spot the tiny hole which was causing water to leech into the bathroom.
PVC plumbing is great stuff. Virtually nothing will stick to it so the ol' pipes do flow freely. My 5 Minute epoxy fix on the PVC drain... didn't!

Up to the local Ace store and lo n' behold, there's a new product
Ace Plastic Repair Epoxy. Said to bond ABS (See? I'm getting there), Fiberglass, Hard Plastic, PVC (My fav) and soft plastic.
Perhaps this stuff may be worth a try on the scooter's fender? If it were my fender that was hairlipped, I'd likely put down the epoxy and then bed in some fiberglas cloth for the needed reinforcement.

The epoxy has a
purple label but my digi camera turned it blue. Another idea to choose from.
Monte