Killing spores in smelly shoes?

[Marc Anton]

I have a couple pair of shoes that somehow got contaminated
with what I take to be a fungi of some kind.  None of my other
shoes, nor my feet, smell.  I've tried washing these shoes with soap and 
water but the smell keeps coming back.  I even tried a dilute
bleach solution and left them there for a couple days, left them out to 
dry in the sun for another few days, but a few days later after wearing 
them the smell came back.  I never let my socks, feet, or shoes get too 
moist, and I change my socks every day.  Again, no problem with any of my 
other shoes.  I figure there have got to be some kind of spores hiding 
out in these shoes because after washing them they don't smell, but as 
soon as I begin wearing them the smell comes back again.

I'd like to keep these shoes because they are 
pretty good quality and not that old.  I went bowling a couple times and 
rented shoes, I figure my socks got contaminated then, or they may have 
gotten contaminated when someone tried them on at the shoe store before I 
bought them.  I think it was the rented bowling shoes that contaminated 
one of my shoes because for a good long time after I bought them they 
didn't have that smell.

Any suggestions would be appreciated.
I prefer some kind of natural or "green" solution if possible.

Thanks.

-Marc