Garly_, I had a look at the link. I doubt any weld, goop, or mechanical repair would stand up in a pressurized plastic vessel. It's almost certainly a waste of your time and money. Plus there is the risk of a leak affecting the operator -- small if it's dilute Roundup, but considerably larger if it's a full-blown pesticide/insecticide. My honest advice is to replace or abandon that tank. It's just not worth it. Sorry.

It's not pressurized. I think it is worth a couple bucks worth of glue to try to fix.

My mistake! If it's not pressurized, it's worth a try.