You can find extra copies of certain items lying around in Mushroom Zones, so it should be possible to find another shirt.
More specifically (ROT13): Pbcvrf bs gur tvsg fubc vgrzf pna or sbhaq va Pbearerq Jvyqrearff (hccre yrsg mbar va gur Pnirea bs Napvragf). V qba'g xabj rknpgyl jurer n fuveg jbhyq or ohg gurer fubhyq or bar fbzrjurer vs lbh xrrc rkcybevat.
Alternate solution (ROT13): Lbh pna "qhcyvpngr" nal vgrz lbh'ir cerivbhfyl sbhaq ol gnyxvat gb gur guvrs bhgfvqr gur zhfrhz naq fgrnyvat n pbcl bs gur vgrz. Gurer'f bar ovg bs qvnybthr gung vf nssrpgrq ol jurgure lbh'ir fgbyra sebz gur zhfrhz be abg, ohg V qba'g guvax vg ybpxf lbh bhg bs nalguvat ryfr.