I have sat on a pickup tailgate and sanded a needle down to make it richer,beer in one hand and fine sand paper in the other,we were out in the middle of the desert,the bike was too lean and no way to get another needle.
I kept sanding/drinking,then let the bikes owner test till we got it right.
It worked out fine but.........the needle is anodized so it doesnt wear away,once you sand a needle its soft and will probably wear out pretty quick.
Ive also heard of guys clipping a needle to make it shorter and thus richer,Ive never tried it.
Some bikes around at times