  In this paper we present the results of a blind survey for compact sources in
243 Galaxy clusters that were identified using the thermal Sunyaev-Zeldovich
effect (tSZ). The survey was carried out at 90 GHz using MUSTANG2 on the Green
Bank telescope and achieved a $5\sigma$ detection limit of 1 mJy in the center
of each cluster. We detected 24 discrete sources. The majority (18) of these
correspond to known radio sources, and of these, 5 show signs of significant
variability, either with time or in spectral index. The remaining sources have
no clear counterparts at other wavelengths. Searches for galaxy clusters via
the tSZ effect strongly rely on observations at 90 GHz, and the sources found
have the potential to bias mass estimates of clusters. We compare our results
to the simulation Websky that can be used to estimate the source contamination
in galaxy cluster catalogs. While the simulation showed a good match to our
observations at the clusters' centers, it does not match our source
distribution further out. Sources over 104" from a cluster's center bias the
tSZ signal high, for some of our sources, by over 50%. When averaged over the
whole cluster population the effect is smaller but still at a level of 1 to 2%.
We also discovered that unlike previous measurements and simulations we see an
enhancement of source counts in the outer regions of the clusters and fewer
sources than expected in the centers of this tSZ selected sample.
