Home garnders often loose their hand tools in over-grown grass, weeds,
or bushes.  Using a simple RF transmitter/receiver and antenna,
gardeners might be able to locate lost hand tools that previously had
a "liquid" applied to the plastic handles.  Thus, I'm looking for a
list of 5+ liquid substances that have the following characteristics:

1.  Ability to reflect RF waves (between 1MHz-2GHz) and/or microwaves
2.  Must enfuse or adhere to polymers such as plastic
3.  Preferrably non-toxic
4.  Translucent (clear)

Any help would be greatly appreciated!

Just a couple of thoughts to offer you viligent:

 1. The device would be competing with low-cost metal detectors.
 2. Are you aware of spray-on coatings for RF shielding purposes? The
only one I have some data for gives a nickel coating. It appears to
meet your criteria #1 and #2. The coating can be expected to be
opaque.
 3. Metalic surfaces are the norm when good reflection of
electromagnetic waves is required.

Hope you find these observations of interest.

Maybe some kind of epoxy mixed with small metal beads (I'm talking
really small here!) would do the trick. You probably wouldn't be able
to make it completely translucent but would certainly not be opaque.

What is the business end of the tool made of? If the tools are metal,
even if they are coated, they will probaby make better RF reflectors
than any (safe) add on paint on the handle. Since you want the
opposite of stealth technology, you could look at radar jamming
techniques, like chaff. This is often as simple as trips of aluminum
foil dumped from a plane, but they may have developed some coating for
polymers to get different action out of it.

Aluminized paint (found at industrial supply houses for painting fence
posts) will work. However, it's a silver color.

I don't know of any clear spray product that would do what you want.

Another option is a minaturized tranmitter.

If you change your seeking device for lower RF, then any product with
wax will reflect RF waves.

Metallic sharpie.      I am currently trying to find a similar tech. I
need a key finder that beeps at the hand held unit. Do you know where
I can find one?