Make your own.
As you know from my boring thread on the PAW Forum, I have done this and found it was good fun to do (and relatively inexpensive). Even with my home-made collinear antenna I have received traffic up to 270nm away, so I was pretty pleased with that.
If you look on the FR24 Forum you will see some pretty simple instructions posted by some helpful guys on there. The reason they did this is because I couldn't have told you one end of a Raspberry Pi from the other, let alone what and how I was meant to type into it. As a result of their help I ended up not only feeding FR24 (and receiving a business subscription as a reward for doing so) but, also, a nice radar plot around my location showing all the traffic I was seeing. I know, a tad spotterish, but a bit of harmless fun.
I think when we relocate to the UK at the end of the year I will be setting up my system again. However, my plan will be to (a)set up a PAW OGN-R 'station' and (b)feed the 360Radar site to help them with their Mode S multilateration. If I can feed FR24 as well, using the same gear, then I will do so but I rather think the south coast of England has enough FR24 feeds
I am only hijacking the thread because alexbrett2 answered the OP's query almost straight away.