Hi Rob, I will be seeing you at Cabin Fever and I look forward to that.
Unfortunately I am not the right person to fix your boiler.
If it were me I would get a new boiler.
Ministeam has them as does Matthias Brenner (station500 on eBay)
Wilesco 1662 Toy Steam Engine Part
If you are set on a repair you should show it to Bruce (St Paul Steam)
He will be at Cabin Fever somewhere near me. He may be able to help.
Gil