This is my first tab, so bare with me. It’s pretty simple, though. The lead melody can 
found relatively easily, it’s a traditional song, so it’s public domain, a.k.a. free.

Intro
Em 	G	D	Am	Em	G	D	Em

Verse
Em		    G
Oh, Missis McGrath, the sergeant said,
D		        Am
Would you like a soldier or your son dead?
Em		     G
With a scarlet coat, and a big cocked hat,
D		     Em
Now Missis McGrath, wouldn't you like that?

Chorus
Em		G
Wid yer too-ri-aa, fol de diddle aa
D             Am
Too-ri-oo-ri-oo-ri-aa.
Em		G
Wid yer too-ri-aa, fol de diddle aa
D             Em
Too-ri-oo-ri-oo-ri-aa.

(The rest of the song follows similarly)