  While exoplanets are now routinely detected, the detection of small bodies in
extrasolar systems remains challenging. Since the discovery of sporadic events
interpreted as exocomets (Falling Evaporating Bodies) around $\beta$ Pic in the
early 80s, only $\sim$20 stars have been reported to host exocomet-like events.
We aim to expand the sample of known exocomet-host stars, as well as to monitor
the hot-gas environment around stars with previously known exocometary
activity. We have obtained high-resolution optical spectra of a heterogeneous
sample of 117 main-sequence stars in the spectral type range from B8 to G8. The
data have been collected in 14 observing campaigns expanding over 2 years from
both hemispheres. We have analysed the Ca ii K&H and Na i D lines in order to
search for non-photospheric absorptions originated in the circumstellar
environment, and for variable events that could be caused by outgassing of
exocomet-like bodies. We have detected non-photospheric absorptions towards 50%
of the sample, attributing a circumstellar origin to half of the detections
(i.e. 26% of the sample). Hot circumstellar gas is detected in the metallic
lines inspected via narrow stable absorptions, and/or variable
blue-/red-shifted absorption events. Such variable events were found in 18
stars in the Ca ii and/or Na i lines; 6 of them are reported in the context of
this work for the first time. In some cases the variations we report in the Ca
ii K line are similar to those observed in $\beta$ Pic. While we do not find a
significant trend with the age or location of the stars, we do find that the
probability of finding CS gas in stars with larger vsin i is higher. We also
find a weak trend with the presence of near-infrared excess, and with anomalous
($\lambda$ Boo-like) abundances, but this would require confirmation by
expanding the sample.
