Gun shops.
I've used Birchwood Casey:-
http://www.midwayusa.com/product/419...ue-3-oz-liquid
A little bit goes a very long way. The bottle I have now is still about half full and I bought it maybe 30 years ago.
I suggest that your cousin should do a ring around of gun shops in her area and ask if they stock the stuff.
Its major value is as a touch-up agent, it can help save an old stain job that is looking a bit holey around the edges. You could probably do a complete blade with it, if you exercised care.