Compiling it from source isn't that hard.
To do it, run these commands in terminal:
sudo eopkg it git
git clone https://github.com/prateekmedia/budgie-systemmonitor-applet
cd budgie-systemmonitor-applet
sudo eopkg it budgie-desktop-devel vala -c system.devel libgee-devel libgtop-devel
meson build --prefix=/usr --buildtype=plain
sudo ninja -C build install
After this logout and then login. Open "Budgie Desktop Settings" and add "System monitor" applet.