Bathroom Vent (Update)
https://sfbay.craigslist.org/nby/pts/d/san-rafael-dometic-seitz-mini-heki-plus/7088329494.html
https://www.ebay.com/itm/Dometic-Seitz-Mini-Heki-Plus-Caravan-Campervan-Roof-Light/143331563239
New Craigslist listing from seller in last post, plus one other option in the US for when that one is gone.
Dometic Seitz Mini Heki Plus
$235 eBay "Buy it Now" with free S/H
Hood River, OR
New
This eBay listing appears to be the only easy to buy option without forced ventilation in the US. Also worth noting that a few new Winnebago models now use the Mini Heki instead of the usual Midi Heki (such as the Winnebago ERA 70M). Therefore, a Winnebago dealer could most likely source one. Good in an emergency, as it would most likely be at a higher cost from a dealer. Campervan HQ in Boulder, CO also sells the Mini Heki in the US and has a review from a Sprinter Westfalia owner. However, their product description states it has forced ventilation and is now shipped from Europe.
eBay info:
Dometic Seitz Mini Heki Plus Roof Light
Dometic SEITZ Mini Hekiplus for motorhomes and caravans. Small roof light. Lightly tinted, Insulated dome with single acrylic glazing . Can be opened in three different positions (including a poor weather position). Inner frame with darkening fly screen (can be adjusted separately).
This Roof Light will come with a seal so the rain will not come in when driving. Also know as Non-Forced Ventilation.
Specifications:
Dimensions product depth 20 7/16 "
Dimensions product width 21 "
Net weight 7.28 lbs
Operation is Manual Lever
Fits in a 400 x 400 mm opening.
If you are ordering for a van we highly recommend our roof adapter, item number 143163895340.