We finally received the components we ordered. These are a probe, a pulser+switch+command and an acquisition card.
Probe: We bought it via a contact in the echOpen Slack community at 120€. Here is the site of our contact where the probe is used: https://kelu124.gitbooks.io/echomods/content/ )
Pulser: We ordered the following kit (including the software): https://www.maximintegrated.com/en/products/analog/analog-switches-multiplexers/MAX14808EVKIT.html
We will soon try to command a pulse with the pulser+command and see it on a oscilloscope.