for an intake cover for rain and bug shielding, you could look at tge heating/ventilating supply places. they have intake covers for furnaces and hot water tanks etc that are direct vent as oposed to the old fashioned chimney. usually plastic as thats what the pipes are for those applications, but they may also have some sheet metal ones too. just ensure the screening inside will accomodate the cfm of the engine through all the restirctions of piping etc. maybe even a chimney rain guard or something like that. one of these places probably has a supply cata;ogue with pics, or make a trip to home depot, lol.
some are pretty basic looking and you could fab something up at home , like this one used as a roof cap
https://www.amazon.com.mx/Builders-B...52909807&psc=1