Sears was pushing belts in a matching fabric to their shirts in 1959...
I've got a Tartan J. Press Ribbon belt meself. Why not?
blackwatch tartan wool pants
blackwatch tartan belt
blackwatch minitartan boxers
landsend royal stewart red bd shirt
navy/black/gold argyle socks
pretty snazzy AAAAAAAAGH
Illustrates one of the burdens of carrying the Ivy thing too far. With a lot of belts, that look great, you have to spend an inordinate amount of time trying to be sure that the pattern works with everything else. Seems like a bit too much thought into the garb for the day.
How about a black, tan, and cordo color strap (croc, or calf of your choice), with a sterling slide buckle? You can have the buckle engraved, if you like, and then the choice of the belt becomes simple.
Obviously, with some very casual clothes, you may need a needlepoint, or some such,