If you could stand to have the bottom edge or the cuffs hemmed, that could give you some patching material that you wouldn't have to match colors.
Or, plenty of pictures of patching of clothes using other fabrics. Maybe just a patch of oil-cloth sewn over the hole. Might be a good conversation piece about how you received that bullet hole . . . .
![Wink ;)](https://www.cascity.com/forumhall/Smileys/cowboys/wink.gif)
If you haven't lost any material, just sewing up the tear would work.
The automotive product Armor-All TM would make a good waterproofing sealant to the sewn area.
RCJ