The side wall of the tyre has failed to cause the bump - (but usually egg shaped/sized), and is severely weakened.
DO NOT DRIVE OTHER ON IT OTHER THAN VERY SLOWLY TO NEAREST TYRE FITER AS IT COULD SUDDENLY BURST WITH DIRE CONSEQUENCES.
I would recommend you consider taking it off the car and using your spacesaver, for yours and other road users sakes, but again only to get you to the tyre fitter.
As said by others above, if the other tyre on that axle is in good shape with lots of tread then the replacement should be exactly the same type of tyre. If not and noting your budget is stretched then a pair of Falken 452's is not a bad choice (IMHO Ekona ) for normal road use.
Run-flats are not normally used on 350's, but I expect someone will say they have them.