Brian Lawson has a list of dissenter bapts/births at: www.iomfhs.im/lawsons/dis-births/dis_births.html (you need to read his introduction).
These include:
23 Jun 1839 FAGAN, Hugh Hugh FAGAN/Mary LAUGHLIN R 41
28 May 1847 FAGAN, Margaret John FAGAN/Ellen STOANE R 100
17 Sep 1848 FAGAN, Mary John FAGAN/Ellen SLOANE R 113
13 Feb 1838 FAGAN, Sarah Hugh FAGHAN/Mry LOUGHAN R 33

Civil registration was compulsory in the IoM only from 1878 (births & deaths); 1884 (marriages), so usually only church records before then.

Sue