Pry the floating steel cap off the (ahem) 'breather' and install a piece of 3/8" fuel line and a hose clamp. You can buy the barbed fitting and screw that in, if you want to to extra fancy.
IMO, there is no 'good' Toyota axle breather - they eventually will clog and cause axle or transfer case leaks.
Steve H. - KE0KNH
Colo Springs, CO
'78 FJ40, '89 FJ62, '98 4Runner