The minion shirt I bought from Wal-Mart for about $7 (in the guys section); if they don't sell it at your nearby Wal-Mart perhaps they're online :)
The "that's my minion" shirt I made with a blank t-shirt and iron on letters. The t-shirt was $5 at Michael's store and the iron-ons also at Michael's for about $3
I chose this font because it was the only one that kind of fit into the "evil master" type stuff lol.. though, sorry I cant give you the name of the font- it was ripped off before I bought it.