DaniMac;
Let me add one more Buckle Source. Any tack shop(horse supply store)will sell some very fine brass buckles, in many sizes. They are made to control a Horse, & thus a just dandy for a kilt, & the brass is a nice, different, touch.
For the left, inside closing, I would 2nd Mr.Newscomes' idea of a reversed buckle(thus it does not show, & no hole in the kilt is needed. You can also make a tye closing or velcro.
AsEver
CSA