I assume you dont already have a flight controller? If so then we dont currently sell a stand alone OSD system, as all of ours get info from the flight controller.
We do sell a relatively cheap autopilot kit that can do that here and it includes a OSD and GPS. - https://www.unmannedtechshop.co.uk/apm2-8-autopilot-kit/ You also have the option to add an airspeed sensor, but that is optional, as you get still get ground speed from GPS.
Otherwise I did a quick search on ebay and this is a kit we used to sell that worked well. But we stopped selling it due to the fact that 99% of our customers use flight controllers so having a stand alone system did not sell particularly well.