I'll admit I thought this thread was geared towards OCD, but your post intrigued me. I found that JD labels Clean Funnel brand funnels, which I have never heard of until now. Here's a link showing a variety of their funnels: Keep Grit, Dirt, and Debris Out of Your Equipment with Clean Funnel! - Gear Up With Gregg's - YouTube
I always wad a piece of newspaper in the down the snout after I use a funnel and toss in a covered bucket with the rest of the funnels. The caps would keep things much cleaner, and I really like that they use standard sized caps that can be replaced with other household product caps if lost.
Yeah, it has that OCD feel, I know
I have that funnel that has lids and as a bonus, it's a measuring funnel. You twist the blue spout to open it. Handy when you know how much fluid you need to put in.