I sort of agree with the post "it's your money...do whatever you want".
I got my jacket from Stuff4Greeks and while the bulk of their work seems to be done for NPHC groups, they have samples of many other organizations as well. As far as disrespect or looks....no one organization lays a claim on Greek-lettered clothing. You may be the first to break the mold; but you probably will not receive as much strife as you are envisioning.