Are the flares rubber or some sort of soft plastic. If they are rubber you wont be able to weld them

you may be able to glue the bits in but not sure how that will look when you paint them, pretty crap I think.
If the flares are soft plastic (polypropelyene, polyethelyene or polywantacracker), they can be welded but again how it looks when painted is upto the skill of the welder or if bog will stick. I was a plastic welded/fabricator for about 15 years mostly PVC though.
Try Ausplastics in Keysborough if they are close to you, they do a lot of big stuff so might not be interested in your job, but you never know your luck in a big city