I bought my factory made teardrop doors from Frank Bear at Vintage Technology. You can find them on eBay in two sizes and it's the same price whether you order through eBay or call him direct. He's a super nice guy and will talk and advise you on anything anytime. He sells lots of other parts as well.
The doors are pricey (and heavy) but they are very well built and others who have used them say easy to install (I haven't gotten to that point yet) and completely waterproof. They have a very nice door handle/locking mechanism and a nice size opening window with screen.
I think it's about $240 for the small door and $300 for the large one. I got the large ones for my Benroy. 3/4" trim rings are standard, but they will custom make for any size wall thickness for an extra $20. Allow an extra couple of weeks for a custom trim ring.
(No, I don't know him personally and I have no connection with the company. But I have had good experiences dealing with him so far. )