Plaster of Paris on it’s own does not stand up to heat very well. There are some additives that can help such as flint or grog.
Ceramic moulds work well.
Moulds from vermiculite and hight temperature cement work well too, although bulky.
Ceramic fibre and board moulds are good too.
It all depends on the shapes you wan to achieve and the durability required.
Angel Thwaites has a good book “Mould making for glass” that contains a number of guidelines. (A C Black, London 2011. ISBN 978-14081-1433-9)