There must be an easy way to stick a crude sight onto the barrel even if it's only a temporary one, mostly to guide the elevation.
Maybe wrap a zip tie on the barrel and leave enough of a tail sticking up that can be trimmed to size or something.
Or zip tie a little piece of wood onto the barrel, and then stick a pin in it if you need to.
There should be an easy way that only costs a few cents, like looping a piece of tape around the barrel, sticking the ends together and leaving a tail sticking straight up.
Use it for a few shots and then take it off and throw it away if you don't like it.