I have a one-piece Kohler Rialto (3402) toilet that looks like it needs
a new fill valve. It is leaking around the top. Looks like the unit
is based on a Coast/Master 1Q1X, so I found a new rubber/valve assembly
for the top, and that did not seem to repair it, at least not entirely.
I see that Kohler sells a $102 rebuild kit for the toilet (K-84499),
and indeed, last year I put one of those into another toilet I had that
had a crack in the float valve. It worked, but before I go spend
another $100, I was wondering if there were any alternatives.

Here's the Kohler web-site with documentation on the toilet:

http://www.us.kohler.com/onlinecatalog/pdf/114396_8.pdf

The setup looks like a fairly conventional 8" fill valve/ballcock, but
with a tube out of the side that goes to the rim of the toilet bowl.
The body fastens into the fill valve, and the tube to that. The float
attaches to the body and shuts off flow to the rim. All kind of
ingenious, in a way. But a bit non-standard.

What I was wondering, is if one of the Fluidmaster or Korky replacement
valves would work? They're a heck of a lot cheaper, like $10.

For example, the Korky (Lavelle) Quietfill:

http://www.korky.com/korkyquietfill1.htm

or the Fluidmaster 400A:

http://www.fluidmaster.com/pdf/400a_instructions.pdf

Two parts are not clear to me:

1. Will they fit? (height mostly)
2. Will they work properly? (mostly where does the rim pipe attach)

Any other suggestions?