Just ordered a complete Provent Kit off eBay from Western Filters as there was a '15% off' discount code on the page, so instead of $350 delivered ... it was less than $300 delivered to my door
I think the cost is justified for what it does for the long term ownership viability.
Hopefully buying a complete 'kit' with mounting bracket, all required hoses & fittings proves to be a benefit over hunting around & getting all the required individual parts separately.