Weld-on is an Austrailian product I believe. Just go to your local plastics dealer and tell them what you are doing. They will sell you some cyno-acrylic solvent.
If they are out of stock on needle solvent bottles just head over to a Rockler woodworking store, they sell them for about $3.00.
Practice first and don't pull all th eprotective paper off, just what you need to glue.
Don't worry about sanding too much, just get it good then finish off by flame polishing (practice first). Your job will come out looking great.