My suggestion would be
ABIT's KT7 but there's no way you'll get it for $100 or even close to that price
wein.
You can also take a look at
MSI's K7T Pro some of which are supposed to have an isa bus slot.
Soyo also has
the SY-K7VTA which has an isa bus slot. I haven't seen any reviews of it thus far.