The ferrite beads designed for filtering computer leads are often optimized
for the 50 - 150 MHz range. A couple of those slipped over the coax
should work well enough for your needs.
The frequency range of a balun depends on the stray reactances of the
windings and the core material. G3TXQ gives a number of measurements
of choke baluns on his site: http://www.karinya.net/g3txq/chokes/
The design you linked to is a 1 : 1 voltage
balun. A better approach
is a current
balun, commonly made either by slipping ferrite beads
over the outside of the coax or winding the feedline into a choke coil.
Using coax + ferrite give a particularly wide operating bandwidth - even
at frequencies where the balun isn't effective, at least you are still
feeding the antenna directly through coax, so it will have less effect on
the SWR than a transformer arrangement.
Meawhile there are lots of inexpensive 4 : 1 TV baluns (75 ohms to 300
ohms) around, and you may be able to saw open the case and rewind
the balun core to give a 1 : 1 ratio instead.