Try e-gunparts.com
$80 - $100
Usually $100-$150 for a good condition gun
I've owned both and they are the same physical size.
The serial number is located on the left side of the frame behind the trigger. If you simply do an internet search for 'Iver Johnson TP22' you will bring up multiple pages with pictures of that model. sales@countrygunsmith.net
DO NOT FIRE THIS WEAPON UNTIL A QUALIFIED GUNSMITH HAS REPAIRED IT!!!!!!!!!!!!! DANGER!!!!!!!!!!!!!!!!!\ UNSAFE!!!!!!!!!!!!!!!!!!!!!
First and foremost, make sure you are not limp wristing when you fire. Second, make sure it is clean. Third, try ALL available brands and bullet weight combinations. Fourth, look at the magazine and magazine spring. Fifth, look at the extractor and exctractor spring.