Here are some replacements for Champion UN12Y now updated to some of the following::
Champion UN12Y replacement spark plugs
•Autolite 4265
•Autolite 65
•Autolite XS65
•Autolite XST4265
•Bosch 0241229715
•Bosch 0242229555
•Bosch 0242229656
•Bosch W8DC
•Bosch WR8DC+
•Bosch WR8DP
•Champion N12YC
•Champion OE015
•Champion OE015T10
•NGK 6511
•NGK BP5ES
•NGK stk 6511