I run a hose from my house and have one of these taps.
Is there a connector I can get to connect to the source part of the tap? It's really hard to search for as I can only find tap to hose connectors and not hose to tap fittings.
Confused a bit by your question. Here's the proper terminology and maybe you can come back and refine your question.
The "tap" is the outside faucet where this unit gets attached to. The product you linked to is marketed as a "tap adapter" it is not a tap.
The picture you posted is sold as one unit but is actually 3 separate components.
There is a Y adapter that allows you to to connect three watering fixtures. The top part connects to the tap (hose bib) via a female hose threaded coupling. The two other ends have male hose threads.
There are also 2 male quick release couplings. One end of the QR coupling has female hose threads that allow it to attach to the male hose threads on the Y adapter. The other end is the male quick release fitting. The small type with the black o-ring.
The "source" part just screws onto the tap (hosebib) if you want to be able to quickly attach and detach it from the hose bib you can get a quick release coupling set. It will have a male and female in the set. One goes on the tap, the other screws onto the Y adapter.
If you're asking how do you attach hoses to the Y adapter. You can unscrew the male quick connects and screw the hose on directly. Or you can buy female quick release fittings that attach onto the end of your hose.