We bought my husband a black jacket from Kohl's as a last-minute thing when his grandfather died. However, since he only wears it to funerals and viewings, it's in fabulous shape and hasn't yet needed cleaning. With a pair of black pants, a white shirt, and a nice tie, he always looks appropriate.
I would bet you can find a nice black jacket at a Kohl's or a Burlington Coat Factory for around $75, maybe up to $100. Yes, it sucks to pay that much for something you're not going to need a lot of the time, but I really think that this is one of those situations where you need to be appropriate, particularly if the deceased is part of your immediate family.
Let this be advice to all the Mustachians out there - get yourself a nice black outfit to wear to a funeral and put it in your closet so you have it. Every time you wear it, before you put it away, make sure it's in good working order for next time. If you have a long lead time before you need something like that, you can look for cheap options, but whatever you do, do something. A blogger friend of mine calls this the "Garment Bag of Death," and while that's a little morbid, it gives me personal peace of mind to know that all my stuff is ready to go in case of tragedy.