float/shutoff valves for top bungs of 55gal drum?

Does anyone know if someone makes a float valve that just screws into one of the the bungs on the top of a 55gal drum? I have the black plastic type with a removable top. It'd be nice not to have to drill holes in it and deal with another possible leak point.

Bueller? Bueller? Bueller?

I like to install the floats on bung cap rather that in the barrel side. Shouldn't be a leak hazard. But as far as i know, nobody makes a float that'll just screw right in.

If the float will not fit in the bung cap I'd just drill the hole in the barrel top. the 1/4 float is use for my RO is small enough to be put in a hole drilled right in the center of the bung cap

How do you install it? Most of the ones i see need to be mounted horizontally for the float to work correctly