I've successfully glued up a great many cuts of that size using superglue. Deflate, glue it, clamp the cut closed, give it a while to dry. I get a lot of such cuts because the local stone is flint which chips into tiny glass like shards. Every now and then I deflate the tyre and squeeze it all the way around looking for shards of flint slowly working their way in. I like to think that each one I find is a future flat that I have avoided.