you wont get 50Hz directly out of an SMPS - the whole point is the transformer is a tenth of the linear dimensions times by dint of switching at 50 KHz or so ....
IF the load can tolerate a fairly rough waveform, you may manage an SMPS, rectifying to 130 VDC or so, and then a commutation circuit to make a 50 Hz out of square wave pieces, much as a VFD does.
The light weight car battery to mains inverters do this sort of thing - there is no 50Hz transformer in side, rather the high voltage is generated supersonic frequency and rectified, and then the DC is sliced and diced to fake a 'not very' sinewave.
I suspect what you want is not available as a single item. You may be able to do some cunning with a 110V inverter (though it is likely to be 60Hz) and a lightweight 13V DC supply.
Earthing the centre would have to be via a pair of caps or similar unless the DC centre voltage of the inverter was available..
I suspect it would be quite fun to to do as a project, but I don't think anyone has, and meeting all the other relevant standards to do it properly makes it uneconomic.
Thank you Mike. I suspected that if it were easy, one would be on the market by now! It would have been good not to have to lug a resin encased one round all the time as I'm a 110 V man other than my cordless battery chargers! I suppose if I can still lug a TE80 round and use it, I shouldn't complain.................
