Since I just went through the process of replacing one, thanks to 8.1al, here is his response:
Try this Bingo
http://www.stalkupsrv.com/eshopprod_...Vent_Cap_-.htm
Bingo
On edit: Oh, they are called mushroom attic vents and provide circulation to the open attic portion beneath the rig's roof structure.
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Bingo and Cathy - Our adventures begin in the hills of WV. We are
blessed by our 2014 3850FL Big Sky (previous 2011 3750FL and 2007 3400RL) that we pull with a 2007 Chevy Silverado Classic DRW CC dually.