adam has the scoop,, i sure don’t know what an orpheus is but you can get new jets (orifice) from any dealer of gas and propane products,,

First thing to do is you need to get a gas regulator with hose and a propane tank.THEN most of all find out first if you can get a Orpheus to convert from natural to propane from any propane dealer,which is easy to do and shouldn’t cost to much.

The conversion kit can be found at fireplace shops, maybe home depot.