I've used a Panasonic TUCT20 in the past but they haven't been sold for years. I don't think you will find many Freeview stb's of any make with RF output on sale anymore so you will be best looking for a 2nd hand item on one of the on line auction sites.
Alternatively you could try using an RF modulator with the stb. e.g.
http://www.maplin.co.uk/programmable-universal-modulator-33050
Alternatively you could try using an RF modulator with the stb. e.g.
http://www.maplin.co.uk/programmable-universal-modulator-33050